1 Samuel 21:12-15

21:12 And David laid up these words in his heart, and was sore afraid of Achish the king of Gath. 21:13 And he changed his behaviour before them, and feigned himself mad in their hands, and scrabbled on the doors of the gate, and let his spittle fall down upon his beard. 21:14 Then said Achish unto his servants, Lo, ye see the man is mad: wherefore [then] have ye brought him to me? 21:15 Have I need of mad men, that ye have brought this [fellow] to play the mad man in my presence? shall this [fellow] come into my house?