John Gill Commentary 1 Samuel 13:12

"therefore said I, Now will the Philistines come down upon me to Gilgal, and I have not entreated the favor of Jehovah: I forced myself therefore, and offered the burnt-offering." — 1 Samuel 13:12 (ASV)

Therefore said I .
&c.] 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 offered a burnt offering ;
it was reluctant to him, it was against his will as well as the command of Samuel, to offer before he came, he suggests; but such were the circumstances he was in, that he was obliged to it; these are the reasons or excuses he made, and some of them have a specious appearance in them.