By this great promise of the text is not merely meant that God will lead the converted to know that there is a God, because that may be known without s new heart. Any man possessed of reason may know that there is a Supreme Being, who created all things and preserves the universe in existence. The text promises that the favoured ones shall know that God to be Jehovah. Man fashions for himself a god after his own liking; he makes to himself, if not out of wood or stone, yet out of what he calls his own consciousness, or his cultured thought, a deity to his taste, who will not be too severe with his iniquities, or deal out strict justice to the impenitent. The Holy Spirit, however, when He illuminates the mind, leads us to see that Jehovah is God, and beside Him there is none else. He teaches His people to know that the God of heaven and earth is the God d the Bible, a God whose attributes are completely balanced, mercy attended by justice, love accompanied by holiness, grace arrayed in truth, and power linked with tenderness. When the heart is content to believe in God as He is revealed, and no longer goes about to fashion a deity for itself according to its own fancies and notions, it is a hopeful sign. The main stress of the promise lies, however, in this: "I will give them a heart to know ME"; that is, not merely to know that I am, and that I am Jehovah, but to have a personal knowledge of Myself. It is not enough to know that our Creator is the Jehovah of the Bible, and that He is perfect in character, and glorious beyond thought; but to know God we must have perceived Him, we must have spoken to Him, we must have been made at peace with Him, we must have lifted up our heart to Him, and received communications from Him. If you know the Lord your secret is with Him, and His secret is with you; He has manifested Himself unto you as He does not unto the world. He must have made Himself known unto you by the mysterious influences of His Spirit, and because of this you know Him. I THE SEAT OF THIS KNOWLEDGE "I will give them a heart to know Me." Observe that it is not said, "I will give them a head to know Me." The first and primary impediment to man's knowledge of God lies in the affections The heart is the seat of the blindness; there lies the darkness which beclouds the whole mind. Hence to the heart the light must come, and to the heart that light is promised.

1. I understand by the fact that the knowledge of God here promised lies in the heart, first, that God renews the heart so that it admires the character of God. The understanding perceives that God is just, powerful, faithful, wise, true, gracious, longsuffering, and the like; then the heart being purified admires all these glorious attributes, and adores Him because of them.

2. The heart-knowledge promised in the covenant of grace means, however, much more than approval: grace enables the renewed heart to take another step and appropriate the Lord, saying, "O God, Thou art my God, early will I seek Thee." All the saved ones cry, "This God is our God for ever and ever; He shall be our guide even unto death"

3. All true knowledge of God is attended by affection for Him." In spiritual language to. Know God is to love Him. "He that loveth not knoweth not God, for God is love." It is the great passion of the renewed soul to glorify God, whom he knows and loves; knowledge without love would be a powerless thing, but God has joined this knowledge and love together in a sacred wedlock, and they can never be put asunder. As we love God we know Him, and as we know Him we love Him. Admiration, appropriation, affection are crowned with adhesion. To know a thing by heart is, in our common talk, to know it thoroughly, Memories of the heart abide when all others depart. A mother's love, a wife's fondness, a sweet child's affection, will come before us even in the last hours of life; when the mind will lose its learning and the hand forget its cunning, the dear names of our beloved ones will linger on our lips; and their sweet faces will be before us even when our eyes are dim with the shadow of approaching death. If we can sing, "O God, my heart is fixed, my heart is fixed," then the knowledge which it possesses will never be taken away from it.

II. THE NECESSITY OF THIS KNOWLEDGE.

1. To know God is a needful preparation for every other true knowledge, because the Lord is the centre of the universe, the basis, the pillar, the essential force, the all in all, the fulness of all things. You may learn the doctrines of the Bible, but you do not know them truly till you know the God of the doctrines. You may understand the precepts in the letter of them, and the promises in their outward wording, but neither precept nor promise do you truly know until you know the God from whose lips they fell. The ancient sage said, "Man, know thyself." He spake well, but even for this man must first know his God. I venture to say that no man rightly knows himself till he knows his God, because it is by the light and purity of God that we see our own darkness and sinfulness.

2. The knowledge of God is necessary to any real peace of mind. Suppose a man to be in the world and feel that he is right every way except with regard to God, and as to Him he knows nothing. Hear him say, "I go about the world and see many faces which I can recognise, and I perceive many friends upon whom I can trust, but there is a God somewhere, and I know nothing at all about Him. Whether He be my friend or my foe I know not." If thoughtful and intelligent he must suffer unrest in his spirit, because he will say to himself, "Suppose this God should turn out to be a just God, and I should be a breaker of His laws! What a peril hangs over me. How is it possible for me to be at peace till this dreadful ignorance is removed?" He is the God of peace, and there can be no peace till the soul knows Him.

3. That this knowledge of God is necessary is clear, for how could it be possible for a man to have spiritual life and yet not to know God? If you do not know Him you are not a partaker of His grace, but you abide in darkness Into His heaven you can never enter till He has given you a heart to know Him; do not forget this warning, or trifle with it.

III. THE EXCELLENCY OF THIS KNOWLEDGE.

1. One of the first effects of knowing God in the soul is that it turns out our idols. God so enamours the soul of the converted man, so engrosses every spiritual faculty, that he cannot endure an idol, however dear in former times; and if perchance in some back-sliding moment an earthly love intrudes, it is because the man has withdrawn his eye from the splendour of the Deity.

2. The second good effect of the knowledge of God is that it creates faith in the soul; to prove which I might give a great many texts, but one will suffice (Psalm 9:10): "They that know Thy Name will put their trust in Thee." We cannot trust an unknown God, but when He reveals Himself to us by His Spirit, then to trust Him is no longer difficult; it is, indeed, inevitable.

3. This knowledge of God creates good works also (1 John 2:3). A heart to know the Lord begets and nurtures every virtue and every grace, and is the basis of the noblest character, the food which feeds grace till it matures into glory.

4. To know God has over us a transforming power. Remember how the apostle writes (2 Corinthians 3:18). Every thought which crosses the mind affects it for the better or the worse, every glance is moulding us, every wish fashions the character. A sight of God is the most wonderfully sanctifying influence that can be conceived of. Know God, and you will grow to be like Him.

5. The knowledge of God causes us to praise Him. "In Judah is God known; His name is great in Israel." It is not possible for us to have low thoughts of Him, or to give forth mean utterances concerning Him, or to act in a miserly way towards His cause, when we practically know Him.

6. The knowledge of God brings comfort, and that is a very desirable thing in a world of trouble. What saith the Psalmist? "God is known in her palaces for a refuge."

7. To know God also brings a man great honour. "Because he hath set his love upon Me, therefore will I deliver him: I will set him on high, because e hath known My name." Think of it — "set on high," and set on high by the Lord Himself, and all as the result of knowing the name of the Lord.

8. The man who knows the Lord will have usefulness given him (2 Corinthians 2:14). We cannot teach others of things which we do not know ourselves. If we have no savour in us there cannot be a savour coming out of us. We shall only be a drag upon the Church in any position if we are destitute of the knowledge of God in Christ Jesus; but if we are filled with a knowledge of Christ, then the sweet savour of His name will pour forth from us as perfume from the flowers.

IV. THE SOURCE OF THIS KNOWLEDGE. None but the Creator can give a man a new heart, the change is too radical for any other hand. It would be hard to give a new eye, or a new arm, but a new heart is still more out of the question. The Lord Himself must do it.

1. It is evidently a work of pure grace. He freely gives to whomsoever He wills, according to His own declaration, "I will have mercy on whom I will have mercy."

2. It is evidently a work which is possible. All things are possible to God, and He says, "I will give it to them." He does not speak of it as a blessing desirable, but unattainable; on me contrary He says, "I will give them a heart to know Me"

3. It is a work which the Lord has covenanted to do (Hosea 2:19; Jeremiah 31:32-34).

( C. H. Spurgeon.)