Psalms 52:2

Those that glory in sin, glory in their shame. The patience and forbearance of God are abused by sinners, to the hardening of their hearts in their wicked ways. But the enemies in vain boast in their mischief, while we have God's mercy to trust in. It will not save us from the guilt of lying, to be able to say, there was some truth in what we said, if we make it appear otherwise than it was. The more there is of craft and contrivance in any wickedness, the more there is of Satan in it. When good men die, they are transplanted from the land of the living on earth, to heaven, the garden of the Lord, where they shall take root for ever; but when wicked men die, they are rooted out, to perish for ever. The believer sees that God will destroy those who make not him their strength.

Thy tongue deviseth mischiefs. Thou speakest with an ulterior design. The information given was for Saul's assistance apparently, but in very deed in his heart the Edomite hated the priests of the God of Jacob. It is a mark of deep depravity, when the evil spoken is craftily intended to promote a yet greater evil. Like a sharp razor, working deceitfully. David represents the false tongue as being effectual for mischief, like a razor which, unawares to the person operated on, is making him bald; so softly and deftly do Oriental barbers perform their work. Or he may mean that as with a razor a man's throat may be cut very speedily, under the pretence of shaving him, even thus keenly, basely, but effectually Doeg destroyed the band of the priests. Whetted by malice, and guided by craft, he did his cruel work with accursed thoroughness.