Jepthah made a vow to sacrifice whoever walked out of his front door first when he returned home; the fact that it's his daughter is portrayed as a horrible twist (I guess he was hoping to sacrifice a servant or something? How did this guy not see it coming? Though I just read another interpretation, that he expected it to be one of his animals) and the approval or disapproval of God is not recorded, nor is whether he

The point of the story seems to be that you shouldn't go round making stupid oaths, not that you should sacrifice your children.