The spring in Jezreel is likely a reference to the Spring of Harod, located southeast of the city of Jezreel at the foot of Mount Gilboa.1 Jezreel was located within the land allotted to the tribe of Issachar (Joshua 19:17–18).2 Saul very likely had spies amongst the Philistines who would have told him about the gathering of their armies.3 In response to their reports, he mustered his troops at Jezreel, a place with easy access to food and water.4
1 Now the Philistines had gathered all their forces at Aphek. And the Israelites were encamped by the spring that is in Jezreel.