לְדָוִ֗ד בְּשַׁנּוֹת֣וֹ אֶת־טַ֭עְמוֹ לִפְנֵ֣י אֲבִימֶ֑לֶךְ וַֽ֝יְגָרֲשֵׁ֗הוּ וַיֵּלַֽךְ׃
大衛的詩。那時他在亞比米勒面前改變自己的言談舉止，亞比米勒就把他趕走，他便離去了。
Rashi
when he disguised his sanity as the matter that is stated (in I Sam. 21:14): “And he changed his speech before their eyes, etc. And he scribbled upon the doors of the gates.” That he disguised his speech and his sanity and feigned madness and let his saliva run down upon his beard.
Rashi
before Abimelech All Philistine kings were called thus, and all Egyptian kings [were called] Pharaoh. Although his name was Achish, he was called Abimelech. The Midrash Aggadah explains that he was as righteous as Abimelech (mentioned in the Torah in relation to Sarah), for he did not want to kill him although his men said to him, “Is this not David, the king of the land?” As is stated in Midrash Psalms (34:1).