Psalm 7:4 This is not about wicked people doing to for others: as some may use it to their advantage, seeing how if they help others, they could be excused from any wrong doings elsewhere, or that those that they have helped should not be their judge over any wrong doings. in v.5: David here truly seeks any corruption in his hands. It is clear that the ones offending him were more likely in the wrong with God than the king himself has trespassed God, yet, he is carefully guarding his own hands free from iniquity, to find them pleasing to God.
v. 6-7: It seems that it was a time when the wicked are justifying themselves, making the wrong right and turning right into wrong. In such confusion, David called upon the Lord to return among the people.
v.8: Some would have trouble with this verse, as if David is lifting his own righteousness independent of God. The context is clear, David is aligning himself to the holy God and seeks to be certain of so. Today, it's hard for some to get it, because many fundamentalist preachers have preached a message that is devoid of works. Any human works, they deemed not of God. Following the Gnostic heresy in the dichotomy of flesh and spirit.