Charles Ellicott Commentary 1 Samuel 15:13

"And Samuel came to Saul; and Saul said unto him, Blessed be thou of Jehovah: I have performed the commandment of Jehovah." — 1 Samuel 15:13 (ASV)

Blessed be thou of the Lord.—Saul must have been fully conscious that he had failed to carry out the will and command of the Eternal King of Israel.

In the recent war, undertaken for the definite and solemn purpose of exterminating a wicked and bloodthirsty people whose continued existence inflicted terrible evil on the neighboring countries, Saul had disregarded the express instructions of the prophet of the Lord. For his own covetous purposes, he had not destroyed all but had reserved some of the living spoil for himself.

Conscious of all this, he still dared to come forward and congratulate the prophet on the fulfillment of the Lord’s command. But Saul’s words of self-congratulation were evidently feigned; in his heart, he knew he had been faithless.