1 Samuel 15:12
And when Samuel rose early to meet Saul in the morning, it was told Samuel, saying, Saul came to Carmel, and, behold, he set him up a place, and is gone about, and passed on, and gone down to Gilgal. And when Samuel rose early to meet Saul in the morning, it was told Samuel, saying, Saul came to Carmel, and, behold, he set him up a place, and is gone about, and passed on, and gone down to Gilgal.
The verse belongs to Saul's mission against Amalek, which carried out a sentence delayed for four hundred years. The Amalekites had first attacked Israel in the wilderness, defied God, and practiced idolatry, and God knew they would seek to destroy His people and their worship; their continued wickedness meant the appointed time for judgment had come. God had commanded Saul to destroy everything utterly as a work of justice against Amalek.
Saul disobeyed by sparing the best cattle and sheep to offer as a sacrifice while claiming that he had obeyed, failing to utterly destroy Amalek. His act kindled God's wrath against him and brought judgment upon him. A religious purpose does not excuse disobeying God, because obedience matters more than sacrifice. His conduct illustrates a pattern of self-deception and refusal to acknowledge guilt, in which a person denies wrongdoing until the facts are undeniable, makes no confession, and regards himself as mistreated.