2 Samuel 18:2-3

18:2 David then sent out the army – a third under the leadership of Joab, a third under the leadership of Joab’s brother Abishai son of Zeruiah, and a third under the leadership of Ittai the Gittite. The king said to the troops, “I too will indeed march out with you.”

18:3 But the soldiers replied, “You should not do this! For if we should have to make a rapid retreat, they won’t be too concerned about us. Even if half of us should die, they won’t be too concerned about us. But you are like ten thousand of us! So it is better if you remain in the city for support.”

2 Samuel 21:17

21:17 But Abishai the son of Zeruiah came to David’s aid, striking the Philistine down and killing him. Then David’s men took an oath saying, “You will not go out to battle with us again! You must not extinguish the lamp of Israel!”