1 Samuel 15:11
It repenteth me that I have set up Saul to be king: for he is turned back from following me, and hath not performed my commandments. And it grieved Samuel; and he cried unto the LORD all night. It repenteth me that I have set up Saul to be king: for he is turned back from following me, and hath not performed my commandments. And it grieved Samuel; and he cried unto the LORD all night.
The verse belongs to the account in which Saul was commanded to destroy Amalek utterly. That command was a divine sentence for Amalek's attack on Israel, cruelty, defiance of God, and idolatry, whose execution had been delayed four hundred years because the people had not turned from their sins. God declared regret at setting up Saul to be king because Saul had turned back from following Him and had not performed His commandments.
Saul's disobedience was failure to execute judgment on Amalek and destroy them utterly. He spared the best animals despite God's order to destroy them, while claiming he had obeyed and offering the religious excuse that they were saved for sacrifice. Keeping what God had commanded him to destroy was rejection of God's command. Saul had experienced a change of heart and conversion to God, but under difficulty he did not trust the Lord, and God was testing whether Saul could be trusted with His work as king.
His disregard of God's will showed he could not be trusted with royal power. It revealed that he did not clearly distinguish sacred things, recognize that God's requirements were supreme, or properly value the word given through God's faithful servant. God's declaration of regret meant a change in circumstances and relations with Saul because of Saul's turning away, not a change of mind or a change in God's requirements. The judgment on Saul teaches that apparent economy or a religious purpose cannot justify transgression, that obedience matters more than sacrifice, and that means gained through breaking God's law will ultimately be scattered.
Samuel was deeply grieved by God's message and cried to the Lord all night. He pleaded through the night for the sentence against Saul to be reversed, foresaw that Israel would soon face a trial under a king like the surrounding nations, and was not reconciled to the message he had to deliver but knew he must obey God. His grief and all-night plea mark the seriousness of Saul's failure. The verse applies to one who refuses to receive counsel from God. It applies also to one who denies wrongdoing until the evidence is undeniable, then makes no confession and considers himself mistreated.