1 Blessed is the man who does not walk in the counsel of the wicked or stand in the way of sinners or sit in the seat of mockers.
2 But his delight is in the law of the LORD, and on his law he meditates day and night.
3 He is like a tree planted by streams of water, which yields its fruit in season and whose leaf does not wither. Whatever he does prospers.
4 Not so the wicked! They are like chaff that the wind blows away.
5 Therefore the wicked will not stand in the judgment, nor sinners in the assembly of the righteous.
6 For the LORD watches over the way of the righteous, but the way of the wicked will perish.

Why is this a favourite passage?
The Psalms are wonderful, and this is the first of the psalms – if not pride of place, certainly a prominent place. It sets out two paths – those things which are not to be done, and those things which are to be done. More than this, it sets out the consequences – if we walk in the way of the Lord, pondering his Law (which is one particular embodiment of the Word) then we shall prosper. Obviously there are lots of caveats and explanations needed to put flesh on those stark bones, but here it is portrayed very simply. If we cleave to the Lord, then we gain life.