Why did God stop Abraham but not Jephthah when he sacrificed his daughter?

The Orthodox nuance

The sacrifice of Isaac is a boundary text, but its ending is the key: God stops Abraham's hand. In a world where child sacrifice existed among neighboring peoples, Scripture sets down a powerful sign: the God of Abraham does not feed on the death of the child.

Jephthah is different. He makes a reckless vow, almost pagan in its logic: if I win, I will offer whatever comes out to meet me. The text does not say that God asked this of him. God's silence in the narrative is not moral approval. The Bible sometimes narrates terrible acts precisely to show how far religious man can fall without discernment.

From an Orthodox perspective, a vow does not sanctify evil. Obeying God does not mean carrying out a mad promise that kills an innocent person. True faith has discernment, not zeal alone.