1 Samuel 15:29-33

Also the Glory of Israel will not lie nor change His mind; for He is not a man, that He would change His mind.”

Then Saul said, “I have sinned; but please honor me now before the elders of my people and before all Israel, and go back with me, so that I may worship the Lord your God.”

So Samuel went back following Saul, and Saul worshiped the Lord.

Then Samuel said, “Bring me Agag, the king of the Amalekites.” And Agag came to him cheerfully. And Agag said, “Surely the bitterness of death is gone!”

But Samuel said, “As your sword has made women childless, so shall your mother be childless among women.” And Samuel cut Agag to pieces before the Lord at Gilgal.