'Take an Oath' in the Bible

But the men of Israel were hard-pressed that day, because Saul had put the people under a curse, saying, “Cursed be the man who eats food before evening, and before I have taken vengeance on my enemies.” So none of the people ate any food.

Then one of the people responded: "Your father strictly ordered the army to take an oath. That's why he said, "Cursed is the person who eats food today,' and so the army is exhausted."