David was the penman of most of the psalms, but some evidently were composed by other writers, and the writers of some are doubtful. But all were written by the inspiration of the Holy Ghost; and no part of the Old Testament is more frequently quoted or referred to in the New. Every psalm either points directly to Christ, in his person, his character, and offices; or may lead the believer's thoughts to Him. And the psalms are the language of the believer's heart, whether mourning for sin, thirsting after God, or rejoicing in Him. Whether burdened with affliction, struggling with temptation, or triumphing in the hope or enjoyment of deliverance; whether admiring the Divine perfections, thanking God for his mercies, mediating on his truths, or delighting in his service; they form a Divinely appointed standard of experience, by which we may judge ourselves. Their value, in this view, is very great, and the use of them will increase with the growth of the power of true religion in the heart. By the psalmist's expressions, the Spirit helps us to pray. If we make the psalms familiar to us, whatever we have to ask at the throne of grace, by way of confession, petition, or thanksgiving, we may be assisted from thence. Whatever devout affection is working in us, holy desire or hope, sorrow or joy, we may here find words to clothe it; sound speech which cannot be condemned. In the language of this Divine book, the prayers and praises of the church have been offered up to the throne of grace from age to age.

The holiness and happiness of a godly man. (1-3) The sinfulness and misery of a wicked man, The ground and reason of both. (4-6)

1-3 To meditate in God's word, is to discourse with ourselves concerning the great things contained in it, with close application of mind and fixedness of thought. We must have constant regard to the word of God, as the rule of our actions, and the spring of our comforts; and have it in our thoughts night and day. For this purpose no time is amiss.

4-6 The ungodly are the reverse of the righteous, both in character and condition. The ungodly are not so, ver. 4; they are led by the counsel of the wicked, in the way of sinners, to the seat of the scornful; they have no delight in the law of God; they bring forth no fruit but what is evil. The righteous are like useful, fruitful trees: the ungodly are like the chaff which the wind drives away: the dust which the owner of the floor desires to have driven away, as not being of any use. They are of no worth in God's account, how highly soever they may value themselves. They are easily driven to and fro by every wind of temptation. The chaff may be, for a while, among the wheat, but He is coming, whose fan is in his hand, and who will thoroughly purge his floor. Those that, by their own sin and folly, make themselves as chaff, will be found so before the whirlwind and fire of Divine wrath. The doom of the ungodly is fixed, but whenever the sinner becomes sensible of this guilt and misery, he may be admitted into the company of the righteous by Christ the living way, and become in Christ a new creature. He has new desires, new pleasures, hopes, fears, sorrows, companions, and employments. His thoughts, words, and actions are changed. He enters on a new state, and bears a new character. Behold, all things are become new by Divine grace, which changes his soul into the image of the Redeemer. How different the character and end of the ungodly!

Commentary by Matthew Henry, 1710.