1 Samuel 21:11-13 Good News Bible Anglicised (GNBDC)

11. The king's officials said to Achish, “Isn't this David, the king of his country? This is the man about whom the women sang, as they danced, ‘Saul has killed thousands, but David has killed tens of thousands.’ ”

12. Their words made a deep impression on David, and he became very much afraid of King Achish.

13. So whenever they were around, David pretended to be insane and acted like a madman when they tried to restrain him; he would scribble on the city gates and dribble down his beard.

1 Samuel 21