‘For YHWH knows the way of the righteous,
But the way of the wicked will perish.'
Every man must choose the way in which he walks, whether in the way of the word of God or in the way of sinners. And those who walk in the way of His word ‘YHWH knows' (see Genesis 18:19), He reveals Himself to them, He meets with them, and He blesses them. They are His people and they enjoy His presence and His watch over them. And He knows their way. It is the way of life (Psalms 16:11; Proverbs 12:28), it is the way of peace (Isaiah 59:8), it is the everlasting way (Psalms 139:24). So although they may be tested in it they will finally triumph, for He is with them (see Job 23:10).
But the way of the wicked can be described quickly, its end is that they will perish. That is its one certainty. Whatever they may enjoy along the way, and that is not certain, finally they will perish (compare Psalms 73:17). All in which they are involved will be destroyed. Their way is the way of death (Proverbs 14:12).
For this whole psalm compare Jeremiah 17:7-8 where he speaks of those who ‘trust in YHWH' in similar terms. And then he finishes by saying, ‘the heart is deceitful above all things and is desperately sick. Who can know it?', speaking finally of those who have not trusted in YHWH.