YHWH tries the righteous,
But the unrighteous and him who loves violence his soul hates.
On the unrighteous he will rain snares,
Fire and brimstone and burning wind will be the portion of their cup.
For YHWH is righteous. He loves righteousness.
The upright shall behold his face.'
The psalmist finishes with a strong contrast between righteousness and unrighteousness. He is confident that YHWH accounts him righteous and so he will trust YHWH to watch over him and ensure that justice is done. ‘YHWH tries the righteous.' That is, He tries them in order to establish their faithfulness and loyalty, in order that He might then bless them. So what have such to fear? In contrast, however, He tries the unrighteous, those who do not seek to obey His laws, and those who love violence, and He ‘hates' them (has an aversion to them) because of what He finds. So the psalmist can safely leave his enemies to the judgment of God.
Indeed YHWH will rain snares on the unrighteous, and what they ‘drink' will be fire and brimstone and a hot, searing wind such as some miserably experience in the desert. That will be their portion. And this must be so because YHWH, Who is Himself righteous, loves righteousness and hates iniquity, rewarding goodness and punishing sin.
Finally he points out that in contrast to those who must drink of YHWH's anger, the upright look up and see His face. They walk in His presence. And if a man walks in YHWH's presence why should he fear his foes?
Note the parallel between the upright at whom the wicked shoot their arrows (Psalms 11:3), and the upright who walk in His presence and see and behold His face. If we walk with God we should not be surprised that arrows are levelled at us (Ephesians 6:13). For the wicked hate God and all that is of God.
One final point we must remember. It was because of David's situation and because of his position that he could not flee. He had been secretly anointed as the successor to Saul. He was a man of authority. He stood in the court for righteousness. Many looked to him for the future, and his destiny was there. It would not have been right for him to leave until he had no alternative, although when that time came he did flee. There are times when discretion is the better part of valour, but there are others where we must stand firm because so much rides on it. And God will help us to decide which applies when. We are not called on to be foolhardy. But we are called on to trust God in all circumstances.