1 Samuel 21:12-14

Young's Literal Translation

¹² And David layeth these words in his heart, and is exceedingly afraid of the face of Achish king of Gath,

¹³ and changeth his behaviour before their eyes, and feigneth himself mad in their hand, and scribbleth on the doors of the gate, and letteth down his spittle unto his beard.

¹⁴ And Achish saith unto his servants, `Lo, ye see a man acting as a madman; why do ye bring him in unto me?