1 Samuel 21:13-15

13So he changed his behavior before them and feigned madness in their hands; he scratched on the doors of the gate and let his saliva run down his beard.

14Then Achish said to his servants, “Look, you can see that the man is insane! Why have you brought him to me? 15Am I in need of madmen, that you have brought this man to rave in my presence? Must this man come into my house?”