1 Samuel 21:13 in the King James Version
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.
Context
12 David laid up these words in his heart, and was very afraid of Achish the king of Gath.
13 He changed his behavior before them and pretended to be insane in their hands, and scribbled on the doors of the gate, and let his spittle fall down on his beard.
14 Then Achish said to his servants, “Look, you see the man is insane. Why then have you brought him to me?