1 Samuel 21:13-15
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. Then said Achish unto his servants, Lo, ye see the man is mad: wherefore then have ye brought him to me? 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?