Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[232] AND this was the state of David and his followers: but Absalom got together a vast army of the Hebrews to oppose his father, and passed therewith over the river Jordan, and sat down not far off Mahanaim, in the country of Gilead. He appointed Amasa to be captain of all his host, instead of Joab his kinsman: his father was Ithra and his mother Abigail: now she and Zeruiah, the mother of Joab, were David's sisters. But when David had numbered his followers, and found them to be about four thousand, he resolved not to tarry till Absalom attacked him, but set over his men captains of thousands, and captains of hundreds, and divided his army into three parts; the one part he committed to Joab, the next to Abishai, Joab's brother, and the third to Ittai, David's companion and friend, but one that came from the city Gath; and when he was desirous of fighting himself among them, his friends would not let him: and this refusal of theirs was founded upon very wise reasons: "For," said they, "if we be conquered when he is with us, we have lost all good hopes of recovering ourselves; but if we should be beaten in one part of our army, the other parts may retire to him, and may thereby prepare a greater force, while the enemy will naturally suppose that he hath another army with him." So David was pleased with this their advice, and resolved himself to tarry at Mahanaim; and as he sent his friends and commanders to the battle, he desired them to show all possible alacrity and fidelity, and to bear in mind what advantages they had received from him, which, though they had not been very great, yet had they not been quite inconsiderable; and he begged of them to spare the young man Absalom, lest some mischief should befall himself, if he should be killed; and thus did he send out his army to the battle, and wished them victory therein.