וַיְשַׁנּ֤וֹ אֶת־טַעְמוֹ֙ בְּעֵ֣ינֵיהֶ֔ם וַיִּתְהֹלֵ֖ל בְּיָדָ֑ם ויתו [וַיְתָיו֙] עַל־דַּלְת֣וֹת הַשַּׁ֔עַר וַיּ֥וֹרֶד רִיר֖וֹ אֶל־זְקָנֽוֹ׃
И он изменил свое поведение перед ними, и притворился безумным в их руках, и царапал двери ворот, и позволил его плевку упасть на его бороду.
Zohar
Come and behold, When King David was saved from Achish, King of Gat, he said, "The angel of Hashem encamps..." For the Shechinah surrounded him and saved him from Achish, his people, and those who attacked him. As it is written, "וַיִּתְהוֹלֵל (Eng. 'feigned himself mad') in their hands" (I Samuel 21:14). He asks, Why is it written "Vayitholel" rather than 'וַיִּשְׁתַּגֵּעַ', as it is written, "you have brought this fellow to play the mad man (Heb. וַיִּשְׁתַּגֵּעַ) in my presence?" (I Sam. 21:16).