1 Samuel 15:7-11

Saul defeated the Amalekites, from Havilah as far as Shur, which is east of Egypt. He captured Agag the king of the Amalekites alive, though he totally destroyed all [the rest of] the people with the sword. Saul and the people spared Agag and the best of the sheep, the oxen, the fatlings, the lambs, and everything that was good, and they were not willing to destroy them entirely; but everything that was undesirable or worthless they destroyed completely. Then the word of the LORD came to Samuel, saying, “I regret that I made Saul king, for he has turned away from following Me and has not carried out My commands.” Samuel was angry [over Saul’s failure] and he cried out to the LORD all night.