He that {a} walketh uprightly, and worketh righteousness, and speaketh the truth in his heart.

(a) He shows that we cannot call on God unless we trust in him.Psalm 15:2 Parallel Commentaries

Thus Then what is Written, "The Mouth that Lieth...
31. Thus then what is written, "The mouth that lieth, slayeth the soul;" [2351] of what mouth it speaketh, is the question. For in general when the Scripture speaks of the mouth, it signifies the very seat of our conception [2352] in the heart, where is approved and decreed whatever also by the voice, when we speak the truth, is uttered: so that he lieth with the heart who approveth a lie; yet that man may possibly not lie with the heart, who uttereth other than is in his mind, in such sort that …
St. Augustine—On Lying

The Folly of Slander. Part 1.
"He that uttereth slander is a fool."--Prov. x. 18. General declamations against vice and sin are indeed excellently useful, as rousing men to consider and look about them: but they do often want effect, because they only raise confused apprehensions of things, and indeterminate propensions to action; which usually, before men thoroughly perceive or resolve what they should practise, do decay and vanish. As he that cries out "Fire!" doth stir up people, and inspireth them with a kind of hovering …
Isaac Barrow—Sermons on Evil-Speaking, by Isaac Barrow

The King --Continued.
The years thus well begun are, in the historical books, characterized mainly by three events, namely, the bringing up of the ark to the newly won city of David, Nathan's prophecy of the perpetual dominion of his house, and his victories over the surrounding nations. These three hinges of the narrative are all abundantly illustrated in the psalms. As to the first, we have relics of the joyful ceremonial connected with it in two psalms, the fifteenth and twenty-fourth, which are singularly alike not …
Alexander Maclaren—The Life of David

The Ninth Commandment
Thou shalt not bear false witness against thy neighbour.' Exod 20: 16. THE tongue which at first was made to be an organ of God's praise, is now become an instrument of unrighteousness. This commandment binds the tongue to its good behaviour. God has set two natural fences to keep in the tongue, the teeth and lips; and this commandment is a third fence set about it, that it should not break forth into evil. It has a prohibitory and a mandatory part: the first is set down in plain words, the other …
Thomas Watson—The Ten Commandments

Question Lxxxi of the virtue of Religion
I. Does the Virtue of Religion Direct a Man To God Alone? S. Augustine, sermon, cccxxxiv. 3 " on Psalm lxxvi. 32 sermon, cccxi. 14-15 II. Is Religion a Virtue? III. Is Religion One Virtue? IV. Is Religion a Special Virtue Distinct From Others? V. Is Religion One of the Theological Virtues? VI. Is Religion To Be Preferred To the Other Moral Virtues? VII. Has Religion, Or Latria, Any External Acts? S. Augustine, of Care for the Dead, V. VIII. Is Religion the Same As Sanctity? Cardinal Cajetan, …
St. Thomas Aquinas—On Prayer and The Contemplative Life

Rules to be Observed in Singing of Psalms.
1. Beware of singing divine psalms for an ordinary recreation, as do men of impure spirits, who sing holy psalms intermingled with profane ballads: They are God's word: take them not in thy mouth in vain. 2. Remember to sing David's psalms with David's spirit (Matt. xxii. 43.) 3. Practise St. Paul's rule--"I will sing with the spirit, but I will sing with the understanding also." (1 Cor. xiv. 15.) 4. As you sing uncover your heads (1 Cor. xi. 4), and behave yourselves in comely reverence as in the …
Lewis Bayly—The Practice of Piety

Election Confirmed by the Calling of God. The Reprobate Bring Upon Themselves the Righteous Destruction to which they are Doomed.
1. The election of God is secret, but is manifested by effectual calling. The nature of this effectual calling. How election and effectual calling are founded on the free mercy of God. A cavil of certain expositors refuted by the words of Augustine. An exception disposed of. 2. Calling proved to be free, 1. By its nature and the mode in which it is dispensed. 2. By the word of God. 3. By the calling of Abraham, the father of the faithful. 4. By the testimony of John. 5. By the example of those who …
John Calvin—The Institutes of the Christian Religion

Psalms
The piety of the Old Testament Church is reflected with more clearness and variety in the Psalter than in any other book of the Old Testament. It constitutes the response of the Church to the divine demands of prophecy, and, in a less degree, of law; or, rather, it expresses those emotions and aspirations of the universal heart which lie deeper than any formal demand. It is the speech of the soul face to face with God. Its words are as simple and unaffected as human words can be, for it is the genius …
John Edgar McFadyen—Introduction to the Old Testament