Jamieson, Fausset and Brown on 1 Samuel 13:9-14

9-14. Saul said, Bring hither a burnt offering to me, and peace offerings--Saul, though patriotic enough in his own way, was more ambitious of gaining the glory of a triumph to himself than ascribing it to God. He did not understand his proper position as king of Israel; and although aware of the restrictions under which he held the sovereignty, he wished to rule as an autocrat, who possessed absolute power both in civil and sacred things. This occasion was his first trial. Samuel waited till the last day of the seven, in order to put the constitutional character of the king to the test; and, as Saul, in his impatient and passionate haste knowingly transgressed (1Sa 13:12) by invading the priest's office and thus showing his unfitness for his high office (as he showed nothing of the faith of Gideon and other Hebrew generals), he incurred a threat of the rejection which his subsequent waywardness confirmed.