When Saul heard their words, the Spirit of God came powerfully upon him

 1 Samuel 11:1-15

When Saul heard their words, the Spirit of God came powerfully upon him, and he burned with anger. He took a pair of oxen, cut them into pieces, and sent the pieces by messengers throughout Israel, proclaiming, “This is what will be done to the oxen of anyone who does not follow Saul and Samuel.” Then the terror of the Lord fell on the people, and they came out together as one. When Saul mustered them at Bezek, the men of Israel numbered three hundred thousand and those of Judah thirty thousand.

They told the messengers who had come, “Say to the men of Jabesh Gilead, ‘By the time the sun is hot tomorrow, you will be rescued.’” When the messengers went and reported this to the men of Jabesh, they were elated. They said to the Ammonites, “Tomorrow we will surrender to you, and you can do to us whatever you like.”

When Saul heard their words, the Spirit of God came powerfully upon him, and he burned with anger. 

The next day Saul separated his men into three divisions; during the last watch of the night they broke into the camp of the Ammonites and slaughtered them until the heat of the day. Those who survived were scattered, so that no two of them were left together.

 But Saul said, “No one will be put to death today, for this day the Lord has rescued Israel.”

Then Samuel said to the people, “Come, let us go to Gilgal and there renew the kingship.” So all the people went to Gilgal and made Saul king in the presence of the Lord. There they sacrificed fellowship offerings before the Lord, and Saul and all the Israelites held a great celebration.

Why?

For the Lord is with Saul so Saul can lead the whole Israelites and defeat Ammonites. Rescued Gilead and Samuel let Saul renew the kingship.

Because Saul led the Israelites to defeat the Ammonites, so more people subdued Saul and Saul became the king of Israel.

No one will be put to death today, for this day the Lord has rescued Israel and helped Saul conquer Ammonite, so even there were some scoundrels who said, “How can this fellow save us?” They despised him and brought him no gifts. it is written in chap 10 verse 26.

How?

When Saul heard their words, the Spirit of God came powerfully upon him. This is the power of the Lord with Saul so he can conquer the enemies.