The importance and necessity of making this our great business will manifestly appear from several considerations:

1. The glory of God is much concerned. Heart-evils are very provoking evils to the Lord. The Schools correctly observe, that outward sins are " sins of great infamy:" but that the heart-sins are " sins of deeper guilt." How severely has the great God declared his wrath from heaven against heart-wickedness! The crime for which the old world stands indicted is heart-wickedness! " God saw that every imagination of their hearts was only evil, and that continually;" for which he sent the most dreadful judgments that were ever inflicted since time began. We find not their murders, adulteries, blasphemies, (though they were defiled with these) particularly alleged against them; but the evils of their hearts. That by which God was so provoked as to give up his peculiar inheritance into the enemy's hand, was the evil of their hearts. " O Jerusalem, wash thine heart from wickedness, that thou mayest be saved; how long shall thy vain thoughts lodge within thee?"

Of the wickedness and vanity of their thoughts God took particular notice; and because of this the Chaldeans must come upon them, " as a lion from his thicket, and tear them to pieces." For the sin of thoughts it was that God threw down the fallen angels from heaven, and still keeps them in "everlasting chains " to the judgment of the great day; by which expression is not obscurely intimated some extraordinary judgment to which they are reserved; as prisoners that have most irons laid upon them may be supposed to be the greatest malefactors. And what was their sin? Spiritual wickedness. Merely heart-evils are so provoking to God, that for them he rejects with indignation all the duties that some men perform. " He that killeth an ox is as if he slew a man; he that sacrifices a lamb, as if he cut off a dog's neck; he that offereth an oblation, as if he offered swine's blood; he that burneth incense, as if he blessed an idol." In what words could the abhorrence of a creature's actions be more fully expressed by the holy God? Murder and idolatry are not more vile in his account, than their sacrifices, though materially such as himself appointed. And what made their sacrifices so vile? The following words inform us: "Their soul delighteth in their abominations."

Such is the vileness of mere heart-sins, that the Scriptures sometimes intimate the difficulty of pardon for them. The heart of Simon Magus was not right, he had base thoughts of God, and of the things of God: the apostle bade him " repent and pray, if perhaps the thoughts of his heart might be forgiven him." O then never slight heart evils! For by these God is highly wronged and provoked. For this reason let every Christian keep his heart with all diligence.

2. The sincerity of our profession much depends upon the care we exercise in keeping our hearts. Most certainly, that man who is careless of the frame of his heart, is but a hypocrite in his profession, however eminent he be in the externals of religion. We have a striking instance of this in the history of Jehu. " But Jehu took no heed to walk in the ways of the Lord God of Israel with his heart." The context gives an account of the great service performed by Jehu against the house of Ahab and Baal, and also of the great temporal reward given him by God for that service, even that his children, to the fourth generation, should sit upon the throne of Israel. Yet in these words Jehu is censured as a hypocrite: though God approved and rewarded the work, yet he abhorred and rejected the person that did it, as hypocritical. Wherein lay the hypocrisy of Jehu? In this; he took no heed to walk in the ways of the Lord with his heart; that is, he did all insincerely and for selfish ends: and though the work he did was materially good, yet he, not purging his heart from those unworthy selfish designs in doing it, was a hypocrite. And though Simon Magus appeared such a person that the apostle could not regularly reject him, yet his hypocrisy was quickly discovered. Though he professed piety and associated himself with the saints, he was a stranger to the mortification of heart-sins. " Thy heart is not right with God." It is true, there is great difference between Christians themselves in their diligence and dexterity about heart work; some are more conversant with, and more successful in it than others: but he that takes no heed to his heart, that is not careful to order it aright before God, is but a hypocrite. " And they come unto thee as the people cometh, and they sit before thee as my people, and they hear thy words, but they will not do them: for with their mouth they show much love, but their heart goeth after their covetous." Here was a company of formal hypocrites, as is evident from that expression, as my people; like them, but not of them. And what made them so? Their outside was fair; here were reverent postures, high professions, much seeming delight in ordinances; " thou art to them as a lovely song:" yea; but for all that they kept not their hearts with God in those duties; their hearts were commanded by their lusts, they went after their covetousness. Had they kept their hearts with God, all had been well: but not regarding which way their hearts went in duty, there lay the essence of their hypocrisy.

If any upright soul should hence infer, 'I am a hypocrite too, for many times my heart departs from God in duty; do what I can, yet I cannot hold it close with God:' I answer, the very objection carries in it its own solution. Thou sayest, 'Do what I can, yet I cannot keep my heart with God.' Soul, if thou doest what thou canst, thou hast the blessing of an upright, though God sees good to exercise thee under the affliction of a discomposed heart.

There still remains some wildness in the thoughts and fancies of the best to humble them; but if you find a care before to prevent them, and opposition against them when they come, and grief and sorrow afterward, you find enough to clear you from the charge of reigning hypocrisy. This precaution is seen partly in laying up the word in thy heart to prevent them. " Thy word have I hid in mine heart, that I might not sin against thee." Partly in your endeavors to engage your heart to God; and partly in begging preventing grace from God in your commencement of duty. It is a good sign to exercise such precaution. And it is an evidence of uprightness, to oppose these sins in their first rise. "I hate vain thoughts." " The spirit lusteth against the flesh." Thy grief also discovers the uprightness of thy heart. If with Hezekiah thou art humbled for the evils of thy heart, thou hast no reason, from those disorders, to question the integrity of it; but to suffer sin to lodge quietly in the heart, to let thy heart habitually and without control wander from God, is a sad, a dangerous symptom indeed.

3. The beauty of our conversation arises from the heavenly frame of our spirits. There is a spiritual lustre and beauty in the conversation of saints. "The righteous is more excellent than his neighbor;" saints shine as the lights of the world; but whatever lustre and beauty is in their lives, comes from the excellency of their spirits; as the candle within puts lustre upon the lantern in which it shines. It is impossible that a disordered and neglected heart should ever produce well ordered conversation; and since (as the text observes) the issues or streams of life flow out of the heart as their fountain, it must follow, that such as the heart is, the life will be. Hence 1 Peter, 2: 12, "Abstain from fleshly lustsóhaving your conversation honest," or beautiful, as the Greek word imports. So Isaiah, 55: 7. " Let the wicked forsake his way, and the unrighteous man his thoughts." His way, denotes the course of his life; his thoughts, the frame of his heart: and therefore since the course of his life flows from his thoughts, or the frame of his heart both, or neither will be forsaken. The heart is the source of all actions; these actions are virtually and radically contained in our thoughts; these thoughts being once made up into affections, are quickly made out into suitable actions. If the heart lie wicked, then, as Christ says, " Out of the heart proceed evil thoughts, murders," &c. Mark the order: first, wanton or revengeful thoughts; then unclean, or murderous practices. And if the heart be holy, then it is as with David: " My heart is inditing a good matteróI speak of the things which I have made touching the king; my tongue is as the pen of a ready writer." Here is a life richly beautified with good works, some ready madeó I will speak of the things which I have made; others makingómy heart is inditing; both proceed from the heavenly frame of his heart. Put the heart in frame and the life will quickly discover that it is so. It is not very difficult to discern, by the performances and converse of Christians, what frames their spirits are in. Take a Christian in a good frame, and how serious, heavenly and profitable will his conversation and religious exercises be! What a lovely companion is he during the continuance of it! It would do any one's heart good to be with him at such a time. " The mouth of the righteous speaketh wisdom, and his tongue talketh of judgment; he law of his God is in his heart." When the heart is up with God, and full of God, how dextrously will he insinuate spiritual discourse, improving every occasion and advantage to some heavenly purpose! Few words then run to waste. And what can be the reason that the discourses and duties of many Christians are become so frothy and unprofitable, their communion both with God and with one another becomes as a dry stalk, but this, their heard are neglected? Surely this must be the reason of it, and it is an evil greatly to be bewailed. Thus the attracting beauty that was wont to shine, from the conversation of the saints, upon the faces and consciences of the world, (which, if it did not allure and bring them in love with the ways of God, at least left a testimony in their consciences of the excellency of those men and of their ways,) is in a great measure lost, to the unspeakable detriment of religion. Time was, when Christians conducted in such a manner that the world stood gazing at them. Their life and language were of a different strain from those of others, their tongues discovered them to be Galileans wherever they came. But now, since vain speculations and fruitless controversies have so much obtained, and heart-work, practical godliness is so much neglected among professors, the case is sadly altered: their discourse is become like other men's; if they come among you now, they may "hear every man speak in his own language." And I have little hope to see this evil redressed, and the credit of religion repaired, till Christians do their first works, till they apply again to heart-work: when the salt of heavenly-mindedness is cast into the spring, the streams will run more clear and more sweet.

4. The comfort of our souls much depends upon the keeping of our hearts; for he that is negligent in attending to his own heart, is, ordinarily, a great stranger to assurance, and the comforts following from it. Indeed if the Antinomian doctrine were true, which teaches you to reject all marks and signs for the trial of your condition, telling you that it is the Spirit that immediately assures you, by witnessing your adoption directly, without them; then you might be careless of your hearts, yea, strangers to them, and yet no strangers to comfort: but since both Scripture and experience confute this, I hope you will never look for comfort in this unscriptural way. I deny not that it is the work and office of the Spirit to assure you; yet I confidently affirm, that if ever you attain assurance in the ordinary way wherein God dispenses it, you must take pains with your own hearts. You may expect your comforts upon easier terms, but I am mistaken if ever you enjoy them upon any other: give all diligence; prove yourselves; this is the scriptural method. A distinguished writer, in his treatise on the covenant, tells us that he knew a Christian who, in the infancy of his Christianity, so vehemently panted after the infallible assurance of God's love, that for a long time together he earnestly desired some voice from heaven; yea, sometimes walking in the solitary fields, earnestly desired some miraculous voice from the trees and stones there: this, after many desires and longings was denied; but in time a better was afforded in the ordinary way of searching the word and his own heart. An instance of the like nature another learned person gives us of one that was driven by temptation upon the very borders of despair; at last, being sweetly settled and assured, one asked him how he attained it, he answered, "Not by any extraordinary revelation, but by subjecting my understanding to the Scriptures, and comparing my heart with them." The Spirit, indeed, assures by witnessing our adoption; and he witnesses in two ways. One way is, objectively, that is, by producing those graces in our souls which are the conditions of the promise; and so the Spirit, and his graces in us, are all one: the Spirit of God dwelling in us, is a mark of our adoption. Now the Spirit can be discerned, not in his essence, but in his operations; and to discern these, is to discern the Spirit; and how these can be discerned without serious searching and diligent watching of the heart I cannot imagine. The other way of the Spirit's witnessing is effectively, that is, by irradiating the soul with a grace discovering light, shining upon his own work; and this, in order of nature, follows the former work: he first infuses the grace, and then opens the eye of the soul to see it. Now, since the heart is the subject of that infused grace, even this way of the Spirit's witnessing includes the necessity of carefully keeping our own hearts. For,

1. A neglected heart is so confused and dark, that the little grace which is in it is not ordinarily discernible: the most accurate and laborious Christians sometimes find it difficult to discover the pure and genuine workings of the Spirit in their hearts. How then shall the Christian who is comparatively negligent about heart-work, be ever able to discover grace? Sincerity! which is the thing sought, lies in the heart like a small piece of gold on the bottom of a river; he that would find it must stay till the water is clear, and then he will see it sparkling at the bottom. That the heart may be clear and settled, how much pains and watching, care and diligence, are requisite!

2. God does not usually indulge negligent souls with the comforts of assurance; he will not so much as seem to patronise sloth and carelessness. He will give assurance, but it shall be in his own way; his command has united our care and comfort together. Those are mistaken who think that assurance may be obtained without labor. Ah! How many solitary hours have the people of God spent in heart-examination! How many times have they looked into the word, and then into their hearts! Sometimes they thought they discovered sincerity, and were even ready to draw forth the triumphant conclusion of assurance; then comes a doubt they cannot resolve, and destroys it all: many hopes, and fears, doubtings and reasonings, they have had in their own breasts before they arrived at a comfortable settlement. But suppose it possible for a careless Christian to attain assurance, yet it is impossible for him long to retain it; for it is a thousand to one if those whose hearts are filled with the joys of assurance, long retain those joys, unless extraordinary care be used. A little pride, vanity, or carelessness will dash to pieces all that for which they have been a long time laboring in many a weary duty. Since then the joy of our life, the comfort of our souls, rises and falls with our diligence in this work, keep your heart with all diligence.

5. The improvement of our graces depends on the keeping of our hearts. I never knew grace to thrive in a careless soul. The habits and roots of grace are planted in the heart; and the deeper they are rooted there, the more flourishing grace is. In Eph.3: 17, we read of being "rooted " in grace; grace in the heart is the root of every gracious word in the mouth, and of every holy work in the hand. It is true, Christ is the root of a Christian, But Christ is the originating root, and grace a root originated, planted, and influenced by Christ; accordingly, as this thrives under divine influences, the acts of grace are more or less fruitful or vigorous. Now, in a heart not kept with care and diligence, these fructifying influences are stopped and cut offómultitudes of vanities break in upon it, and devour its strength; the heart is, as it were, the enclosure, in which multitudes of thoughts are fed every day; a gracious heart, diligently kept, feeds many precious thoughts of God in a day. " How precious are thy thoughts unto me, O God! How great is the sum of them! If I should count them, they are more in number than the sand: when I awake, I am still with thee." And as the gracious heart nourishes them, so they refresh and feast the heart. "My soul is filled as with marrow and fatness while I think upon thee," &c. But in the disregarded heart, multitudes of vain and foolish thoughts are perpetually working, and drive out those spiritual thoughts of God by which the soul should be refreshed. Besides, the careless heart profits nothing by any duty or ordinance it performs or attends upon, and yet these are the conduits of heaven, whence grace is watered and made fruitful. A man may go with a heedless spirit from ordinance to ordinance, abide all his days under the choicest teaching, and yet never he improved by them; for heart-neglect is a leak in the bottomóno heavenly influences, however rich, abide in that soul. When the seed falls upon the heart that lies open and common, like the highway, free for all passengers, the fowls come and devour it. Alas! It is not enough to hear, unless we take heed how we hear; a man may pray, and never be the better, unless he watch unto prayer. In a word, all means are blessed to the improvement of grace, according to the care and strictness we use in keeping our hearts in them.

6. The stability of our souls in the hour of temptation depends upon the care we exercise in keeping our hearts. The careless heart is an easy prey to Satan in the hover of temptation; his principal batteries are raised against the heart; if he wins that he wins all, for it commands the whole man: and alas! how easy a conquest is a neglected heart! It is not more difficult to surprise such a heart, than for an enemy to enter that city whose gates are open and unguarded. It is the watchful heart that discovers and suppresses the temptation before it comes to its strength. Divines observe this to be the method in which temptations are ripened and brought to their full strength. There is the irritation of the object, or that power it has to provoke our corrupt nature; which is either done by the real presence of the object, or by speculation when the object (though absent) is held out by the imagination before the soul. Then follows the motion of the appetite, which is provoked by the fancy representing it as a sensual good. Then there is a consultation in the mind about the best means of accomplishing it. Next follows the election, or choice of the will. And lastly, the desire, or full engagement of the will to it. All this may be done in a few minutes, for the debates of the soul are quick and soon ended: when it comes thus far, the heart is won, Satan has entered victoriously and displayed his colours upon the walls of that royal fort; but, had the heart been well guarded at first, it had never come to thisóthe temptation had been stopped in the first or second act. And indeed there it is stopped easily; for it is in the motion of a soul tempted to sin, as in the motion of a stone falling from the brow of a hillóit is easily stopped at first, but when once it is set in motion "it acquires strength by descending." Therefore it is the greatest wisdom to observe the first motions of the heart, to check and stop sin there. The motions of sin are weakest at first; a little care and watchfulness may prevent much mischief now; the careless heart not heeding this, is brought within the power of temptation, as the Syrians were brought blindfold into the midst of Samaria, before they knew where they were.

I hope that these considerations satisfy my readers that it is important to keep the heart with all diligence. I proceed,