Ambrose of Milan
He then retreated to Etam, near an uninhabited stream, where a rock stood - the fortress of the Judah clan.
And he made a great slaughter of them, so that in astonishment they laid the calf of the leg upon the thigh. And going down he dwelt in a cavern of the rock Etam.
וַיַּ֨ךְ אוֹתָ֥ם שׁ֛וֹק עַל־יָרֵ֖ךְ מַכָּ֣ה גְדוֹלָ֑ה וַיֵּ֣רֶד וַיֵּ֔שֶׁב בִּסְעִ֖יף סֶ֥לַע עֵיטָֽם׃
One Church Father comments on this verse
He then retreated to Etam, near an uninhabited stream, where a rock stood - the fortress of the Judah clan.
Passages read together with this verse.