And they smote the Philistines that day from Michmash to Aijalon: and the people were very faint.

Jamieson-Fausset-Brown Bible Commentary

31-34. the people were very faint. And the people flew upon the spoil-at evening, when the time fixed by Saul had expired. Faint and famishing, the pursuers fell voraciously upon the cattle they had taken, and threw them on the ground to cut off their flesh and eat them raw, so that the army, by Saul's rashness, were defiled by eating blood, or living animals; probably, as the Abyssinians do, who cut a part of the animal's rump, but close the hide upon it, and nothing mortal follows from that wound. They were painfully conscientious in keeping the king's order for fear of the curse, but had no scruple in transgressing God's command. To prevent this violation of the law, Saul ordered a large stone to be rolled, and those that slaughtered the oxen to cut their throats on that stone. By laying the animal's head on the high stone, the blood oozed out on the ground, and sufficient evidence was afforded that the ox or sheep was dead before it was attempted to eat it.

Matthew Henry's Concise Commentary

14:24-35 Saul's severe order was very unwise; if it gained time, it lost strength for the pursuit. Such is the nature of our bodies, that daily work cannot be done without daily bread, which therefore our Father in heaven graciously gives. Saul was turning aside from God, and now he begins to build altars, being then most zealous, as many are, for the form of godliness when he was denying the power of it.