Now the Philistines gathered together all their armies to Aphek: and the Israelites encamped by a fountain which is in Jezreel.
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George Leo Haydock
Aphec. Hence they proceeded to Sunam, and attacked Saul, near the fountain, which were all places in the vale of Jezrahel. The sacred writer thus leaves the two armies ready to engage, being intent on giving the particulars of David's history, and only relating the affairs of Saul, in as much as they may refer to him. (Calmet)
David had retired from the army of the Philistines before Saul went to Endor, and some of the tribe of Manasses went after him, and were present in the battle, in which the Amalecites were slain and plundered, 1 Paralipomenon xii. 19. (Salien)