Abraham Wright, A Practical Commentary on the Psalms (re Ps. 1.1):
Verse 1. Blessed is the man that walketh not in the counsel of the ungodly, nor standeth in the way of sinners, nor sitteth in the seat of the scornful. The first words of the first Psalm, and the last words of the last, are the Prophet David’s Alpha and Omega of knowledge and practice. For he comprehends all that belongs to man’s knowledge, and all that belongs to his practice in those two; first, in understanding true blessedness, and then in praising God for it. David’s Alpha is beatus vir, O the blessedness of righteous men! And his Omega is laudate Dominum, O that men would therefore bless the Lord! And therefore as he begins this book with God’s blessing of man; so he ends it with the man’s praising of God; for where the last stroke of this psaltery, the last verse of the last Psalm is, let every thing that hath breath praise the Lord, yet he adds one note more to us in particular, praise ye the Lord, and there is the end of all.