1 Samuel 14:21

Moreover the Hebrews that were with the Philistines. — These Israelites were, most likely, prisoners who had been compelled to fight against their countrymen, or were levies raised in those parts of the land more immediately under Philistine influence. These, we read, took the first opportunity to go over to Saul. Other Israelites — probably the men of whole villages, who had been compelled, as the result of the late Philistine successes, to desert their homesteads, and seek a precarious living in the hills — joined in the pursuit of the now flying Philistine armies. This is the meaning of the words of the 22nd verse, which speaks of “the men of Israel which had hid themselves in Mount Ephraim.”