1 Samuel 21:2, 13

David said to Ahimelech the priest, “The king has commissioned me with a matter and has told me, ‘Let no one know anything about the matter for which I am sending you and with which I have commissioned you. I have directed the young men to a certain place.’

So [fearing for his life] he changed his behavior in their sight, and acted insanely in their hands, and he scribbled on the doors of the gate, and drooled on his beard.