Judges 11:30

Therefore I have not sinned against you, but you do me wrong to war against me. May the LORD the Judge be judge today between the children of Israel and the children of Ammon.”

However, the king of the children of Ammon didn’t listen to the words of Jephthah which he sent him.

Then the LORD’s Spirit came on Jephthah, and he passed over Gilead and Manasseh, and passed over Mizpah of Gilead, and from Mizpah of Gilead he passed over to the children of Ammon.

then it shall be, that whatever comes out of the doors of my house to meet me when I return in peace from the children of Ammon, it shall be the LORD’s, and I will offer it up for a burnt offering.”

So Jephthah passed over to the children of Ammon to fight against them; and the LORD delivered them into his hand.

He struck them from Aroer until you come to Minnith, even twenty cities, and to Abelcheramim, with a very great slaughter. So the children of Ammon were subdued before the children of Israel.