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.

TITLE, Psalms. See App-63 and the Structures on pp. 720, 721. Compare Luke 20:42 , Luke 24:44 , Acts 1:20 .
BLESSED = How Happy. The first Psalm begins thus and Psalm 2 ends thus. So does the last Psalm of Book I: Psalms 41:1 ; Psalms 41:13 ). Figure of speech Antiptosis ( App-6 ). Compare Jeremiah 17:7 , Jeremiah 17:8 . See App-63 . for the Beatitudes in the Psalms.
man. Hebrew ' ish . Put by Figure of speech Synecdoche (of Species), App-6 , for all of both sexes.
walketh, &c: i.e. who never did walk . . . stand . . . sit. Figure of speech Anabasis , three triplets: walketh counsel ungodly = continue in. standeth way sinners = carry out. sitteth seat scornful = settle down.
ungodly = lawless. Hebrew. rasha'. App-44 .
sinners. Hebrew. chata'.
scornful = scoffers. Hebrew. luz.

2.

But his delight is in the law of the LORD; and in his law doth he meditate day and night.

the law = instruction: i.e. the whole Pentateuch which contains it.
meditate: i.e. continually and habitually.

3.

And he shall be like a tree planted by the rivers of water, that bringeth forth his fruit in his season; his leaf also shall not wither; and whatsoever he doeth shall prosper.

be = become, or prove. Figure of speech Simile. App-6 . Like a tree. The first of two comparisons. See Psalms 1:4 .
planted: i.e. in a garden. Not a "tree of the field".
rivers = divisions irrigating a garden. Hebrew. palgey-mayim. See note on Proverbs 21:1 .
prosper. Compare Genesis 39:3 , Genesis 39:23 .

4.

The ungodly are not so: but are like the chaff which the wind driveth away.

are not so, &c. = not so the ungodly.
like the chaff. The other comparison. See Psalms 1:3 . Compare Psalms 35:5 .
wind. Hebrew. ruach. App-9 .

5.

Therefore the ungodly shall not stand in the judgment, nor sinners in the congregation of the righteous.

stand = rise. No part in first resurrection. Revelation 20:5 , Revelation 20:6 . Compare Psalms 49:14 .
congregation = assembly.
righteous = justified.

6.

For the LORD knoweth the way of the righteous: but the way of the ungodly shall perish.

For. Effect latent in first clause: cause latent in second clause.
knoweth = approveth, or acknowledged. Figure of speech Metonymy (of Cause). Compare Nahum 1:7 . 2 Timothy 2:19 .
perish = come to naught.