1 Samuel 14:24 And the men of Israel were distressed that day: for Saul had adjured the people, saying, Cursed be the man that eateth any food until evening, that I may be avenged on mine enemies. So none of the people tasted any food.
During the victorious rout of the enemy Saul made the army swear an oath that they would not stop fighting to eat food until the evening. The people were tired, hungry, and worn out, so when they heard this command they were distressed, for they needed to eat. But Saul wanted to finish the battle completely that day rather than give thought to the needs of his soldiers.
This was a foolish command from a foolish commander. He was willing to surrender the health and safety of his army to meet his own need for vengeance. His foolishness was evidenced when his own son, Jonathan, paused along the way to eat some honey. When this was found out, Saul had to keep his oath by putting his own son to death, just because he made a rash oath. But the people stopped Saul from doing so and thus rescued Jonathan.
We learn that we should take our promises, oaths, and curses seriously so that we do not make rash oaths and insincere promises. And we do not cause stress in others by making them make a promise. See the story of Herod killing John the Baptist because he made an oath. Or make a note of Jephthah, who killed his daughter because he made an oath.