Willing

Jephthah is an interesting dude. The son of a prostitute, he gets kicked out of the house and goes to live among “worthless fellows”. But in his dealing with the enemies of Israel, he has an encyclopedic knowledge of the history of Israel. He appeals on the basis of what YHWH had done multiple times as he tries to convince the Ammonites to avoid war. Later in the account we learn he had taught the ways of God to his daughter, who submits to his authority despite his rash vow.

God can use anyone to fulfill His purposes who is willing to be used.

Judges 11:12 ESV
[12] Then Jephthah sent messengers to the king of the Ammonites and said, “What do you have against me, that you have come to me to fight against my land?”