It happened on the next day, that an evil spirit from God came mightily on Saul, and he prophesied in the midst of the house: and David played with his hand, as he did day by day. Saul had his spear in his hand;
"Saul raved within his house."  (1 Samuel 18:10).  That `evil spirit' that came upon Saul bore a remarkable resemblance to paranoid insanity; but it was nevertheless a punishment inflicted by God Himself upon the wicked Saul.  David might well have thought that the attempt of Saul to kill him was merely due to a temporary fit of madness, otherwise, he would hardly have exposed himself a second time to Saul's murderous actions.