He took a yoke of oxen, and cut them in pieces, and sent them throughout all the borders of Israel by the hand of messengers, saying, Whoever doesn't come forth after Saul and after Samuel, so shall it be done to his oxen. The dread of Yahweh fell on the people, and they came out as one man.
Saul linked himself with Samuel because Samuel was the recognized spiritual leader of the nation. The Israelites probably dreaded both Saul’s threatened reprisals for not responding to his summons and the Ammonite threat.