2 Samuel 2:11-15

And the time that David was king in Hebron over the house of Judah was seven years and six months. Civil War

Now Abner the son of Ner, went from Mahanaim to Gibeon with the servants of Ish-bosheth the son of Saul.

And Joab the son of Zeruiah and the servants of David went out and met them by the pool of Gibeon; and they sat down, Abner’s men on the one side of the pool and Joab’s men on the other side of the pool.

Then Abner said to Joab, “Now have the young men arise and hold a martial skills match in our presence.” And Joab said, “Have them arise!”

So they got up and went over by count, twelve for Benjamin and Ish-bosheth the son of Saul, and twelve from the servants of David.