I said, ‘Now the Philistines will come down against me at Gilgal, and I have not sought the favor of the LORD.’ So I forced myself, and offered the burnt offering.”
Here is, I. Saul's offence in offering sacrifice before Samuel came. Samuel, when he anointed him, had ordered him to tarry for him seven days in Gilgal, promising that, at the end of those days, he would be sure to come to him, and both offer sacrifices for him and direct him what he should do. This we had Sa1 10:8.
Commenting on 1 Samuel 13:8-14
Therefore said I..... That is, within himself: the Philistines will come down now upon me to Gilgal; on a sudden, unprepared for them, especially in a religious way: and I have not made supplication to the Lord; for his direction and assistance, and for success in the war; which it seems went along with sacrifices, or was implied in them: I forced myself therefore, and...
I forced myself - It was with great reluctance that I did what I did. In all this Saul was sincere, but he was rash, and regardless of the precept of the Lord, which precept or command he most evidently had received, Sa1 13:13. And one part of this precept was, that the Lord should tell him what he should do.