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.

1 Samuel 21:14 Then Achish said to his servants, "Behold, you see the man behaving as a madman. Why do you bring him to me?

1 Samuel 22:1 So David departed from there and escaped to the cave of Adullam; and when his brothers and all his father's household heard of it, they went down there to him.

Touching Jacob, However, that which He did at his Mother's Bidding...
24. Touching Jacob, however, that which he did at his mother's bidding, so as to seem to deceive his father, if with diligence and in faith it be attended to, is no lie, but a mystery. The which if we shall call lies, all parables also, and figures designed for the signifying of any things soever, which are not to be taken according to their proper meaning, but in them is one thing to be understood from another, shall be said to be lies: which be far from us altogether. For he who thinks this, may …
St. Augustine—Against Lying