Charles Ellicott Commentary 1 Samuel 23:3

"And David`s men said unto him, Behold, we are afraid here in Judah: how much more then if we go to Keilah against the armies of the Philistines?" — 1 Samuel 23:3 (ASV)

Here in Judah. —This does not imply that Keilah was outside the territory of Judah, but simply that the district in the neighborhood around Keilah was at that time under Philistine domination. The open country in times of Philistine supremacy first fell under their control; their strongholds, like Keilah, would resist for a much longer period.