A common theme in the things that David writes is for God to take vengeance on the wicked, especially those who are against David in particular. To us this may seem rather barbaric, and it may surprise us when David describes how God does take out his vengeance. However--and this may seem harsh too--it occurred to me that God only punishes those who deserve it. The people being destroyed are those who have brought it upon themselves by their actions. These people are against God, not just unsure if they believe in Him, but actively in opposition to Him. They are described as wicked, sinners, mockers, conspirers, plotters, foes, enemies, arrogant, wrong-doers, liars, bloodthirsty, deceitful, filled with destruction, rebels, etc., and this is just what I saw in the first five Psalms. Most of these traits are things that would make these people hated by men too. If we actually knew them, we might feel like it was right for them to be punished. Most people could say, "good riddance" to evil men.
However, there is a problem. The rest of us "good" people have some of these traits too. What one of us hasn't ever lied? Who hasn't plotted in their heart to strike out at someone who hurt them? Is there anyone who has actually followed every single command of those in authority (this includes listening to our parents, following the speed limit, everything)? The thing is, all of us are sinners, and, really, all of us deserve to die. Even the best of us isn't perfect, even David. In light of this, I love verse 7 of Psalm 5:
But I, by your great mercy,
will come into your house;
in reverence will I bow down
toward your holy temple.
David doesn't get to come into the house of God because he is somehow worthy. Rather, God takes mercy on him, which indicates that there was some offense that God chose to pardon. Mercy is only necessary when someone has done wrong. But we might say, okay, if David is a sinner too, then why does he get mercy when others get vengeance? Well, one clue is that David is bowing down in reverence. Another is in verse 8:
Lead me, O Lord, in your righteousness
because of my enemies--
make straight your way before me.
We can see here that David is actively seeking to be righteous. This doesn't mean that he is always right, but he acknowledges that he needs God to lead him. Instead of plotting against God, which we know from Psalm 2 is a vain endeavor anyway, David, recognizing God's power and authority, is choosing to let God rule him. Let's look at verse 11:
But let all who take refuge in you be glad;
let them ever sing for joy.
Spread your protection over them,
that those who love your name may rejoice in you.
When I read this verse, something that I ask myself is, What do they need protection from? I may be stretching this further than it is intended to go, but I think, honestly, there is only one thing that anyone needs to fear, and that is God. If I am on God's side, I really don't need to fear anything else because He is greater than anything that could hurt me. If I am opposed to God, then I have every reason to be afraid. It follows, then, that I definitely don't want to be on God's bad side. However, since I am imperfect, the only way for me to be right with Him is for Him to lead me and to "make straight [His] way before me." If sin is what causes God's wrath to fall on me, then for me to be "safe," the thing I need protection from is sin.
Yes, there are physical enemies on earth that we need protection from, as well as people who hurt us emotionally. Yes, God is the one to protect us. But, for us to be under God's protection, we need to make sure that we are not the enemy. We are incapable of doing this on our own, so God has to work in us to make us righteous. He will only do that, though, if we let him, so I conclude that the best we can do is to fall helpless before Him, admitting that we can do nothing without Him. Then he will be our refuge.
For surely, O Lord, you bless the righteous;
you surround them with your favor
as with a shield (verse 12).
I encourage you to read all of Psalm 5 again with the idea that we need protection from sin. I think that everyone will be able to relate. I know I did.