1 Samuel 14:21-22

21Now there were Hebrews who had defected to the Philistines previously and had gone up with them to their camp round about—even they joined the Israelites that were with Saul and Jonathan.

22Also when all the men of Israel who had hidden themselves in the hill country of Ephraim heard that the Philistines had fled, they also chased after them in the battle.