Adam Clarke on 1 Samuel 21:15

Shall this fellow come into my house? - I will not take into my service a man who is liable to so grievous a disease. Chandler, who vindicates David's feigning himself, mad, concludes thus: "To deceive the deceiver is in many instances meritorious, in none criminal. And what so likely to deceive as the very reverse of that character which they had so misconstrued? He was undone as a wise man, he had a chance to escape as a madman; he tried, and the experiment succeeded." I confess I can neither feel the force nor the morality of this. Deceit and hypocrisy can never be pleasing in the sight of God.