1 Samuel 21:10-15

Then David arose and fled that day from Saul, and went to Achish king of Gath. But the servants of Achish said to him, “Is this not David the king of the land? Did they not sing of this one as they danced, saying, ‘Saul has slain his thousands, And David his ten thousands’?” David took these words to heart and greatly feared Achish king of Gath. So he disguised his sanity before them, and acted insanely in their hands, and scribbled on the doors of the gate, and let his saliva run down into his beard. Then Achish said to his servants, “Behold, you see the man behaving as a madman. Why do you bring him to me? Do I lack madmen, that you have brought this one to act the madman in my presence? Shall this one come into my house?”