The Hebrew title of this book is 'The Book of Praises'. The term "Psalms" is Greek [psalmoi], taken from the Septuagint, and meaning songs sung to musical instruments. This psalm is a preface to the collection. Hence, in the oldest reading of Acts 13:33, our second psalm is quoted as "the first psalm." One psalms is prefixed as a compendious summary of the whole-God's appointment of salvation to the righteous, perdition to the ungodly, in spite of all present appearances to the contrary.
Blessed - literally, 'Oh the happinesses of the man!' etc. Not merely happy in one respect, but in countless ways (marked by the abstract term, implying that happiness finds its realization only in Him; and by the plural number, implying the manifold aspects of his happiness). [The Hebrew, 'ashreey (H835), happiness, is distinct from baarak (H1288), bless and blessedness].
Walketh ... ungodly ... standeth ... sinners ... sitteth ... scornful - answering respectively to one another in poetical parallelism of thought (the Hebrew principle of versification: see Introduction to Poetical Books); and forming a climax: from "walking in the counsel" (i:e., according to the counsel or plans, Micah 6:16; Psalms 81:12), in the downward steps of sin, one goes on to "standing in the way;" and from this to "sitting in the seat" (Psalms 26:4). From associating with the "ungodly" or 'wicked' [margin, rªshaa`iym (H7563), the root ides of which is disturbance; restlessness (Isaiah 57:20), impelling to continual fresh misdeed: hence, transgression, in act of God's law], one passes to the way of "sinners" [ chªTaa'iym (H2400): literally, those deviating from the straight course; erring, from estrangement of heart and principle]. The crowning of this awful declension is sitting, as in one's habitual place, among. "scorners" (2 Peter 3:3; Isaiah 5:19; Psalms 50:20; Psalms 69:12; Jeremiah 15:17; Jeremiah 17:15). Sitting is the attitude of drinking boon companions. Wine itself is a mocker (Proverbs 20:1).