1 Samuel 15:16
Then Samuel said unto Saul, Stay, and I will tell thee what the LORD hath said to me this night. And he said unto him, Say on. Then Samuel said unto Saul, Stay, and I will tell thee what the LORD hath said to me this night. And he said unto him, Say on.
The verse records Samuel stopping Saul while Saul was claiming to have obeyed God, in order to tell him what the Lord had said to him the night before. Saul's disobedience was sparing the best of the livestock and failing to smite Amalek and utterly destroy them as commanded. The surviving animals exposed that disobedience despite his insistence that he had obeyed, and neither religious intentions nor material gain excused it.
Samuel had spent that night in sorrowful prayer because of Saul's sin. He was indignant and grieving over that sin, yet his love for Saul did not keep him from speaking the needed rebuke. He insisted that Saul hear the message the Lord had given him that night even though he grieved over the disobedience.
Saul bowed his head and invited Samuel to speak, answering Say on. Samuel then spoke with divine authority to deliver God's command concerning Amalek and the Lord's judgment. God's wrath was kindled against Saul because he did not perform the work of justice by smiting Amalek and utterly destroying them. That judgment teaches that obedience to God is better than sacrifice, and that gain obtained by breaking God's law will ultimately be scattered.
The confrontation serves as a pattern for one who denies wrongdoing until the facts leave no room for denial, then makes no true confession and considers himself mistreated. It shows that reproof is a message from God that must be spoken and heard rather than silenced by personal affection or excuses.