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

[21] About this time David was become the father of six sons, born of as many mothers. The eldest was by Ahinoam, and he was called Arenon; the second was Daniel, by his wife Abigail; the name of the third was Absalom, by Maacah, the daughter of Talmai, king of Geshur; the fourth he named Adonijah, by his wife Haggith; the fifth was Shephatiah, by Abital; the sixth he called Ithream, by Eglah. Now while this intestine war went on, and the subjects of the two kings came frequently to action and to fighting, it was Abner, the general of the host of Saul's son, who, by his prudence, and the great interest he had among the multitude, made them all continue with Ishbosheth; and indeed it was a considerable time that they continued of his party; but afterwards Abner was blamed, and an accusation was laid against him, that he went in unto Saul's concubine: her name was Rispah, the daughter of Aiah. So when he was complained of by Ishbosheth, he was very uneasy and angry at it, because he had not justice done him by Ishbosheth, to whom he had shown the greatest kindness; whereupon he threatened to transfer the kingdom to David, and demonstrate that he did not rule over the people beyond Jordan by his own abilities and wisdom, but by his warlike conduct and fidelity in leading his army. So he sent ambassadors to Hebron to David, and desired that he would give him security upon oath that he would esteem him his companion and his friend, upon condition that he should persuade the people to leave Saul's son, and choose him king of the whole country; and when David had made that league with Abner, for he was pleased with his message to him, he desired that he would give this as the first mark of performance of the present league, that he might have his wife Michal restored to him, as her whom he had purchased with great hazards, and with those six hundred heads of the Philistines which he had brought to Saul her father. So Abner took Michal from Phaltiel, who was then her husband, and sent her to David, Ishbosheth himself affording him his assistance, for David had written to him that of right he ought to have this his wife restored to him. Abner also called together the elders of the multitude, the commanders and captains of thousands, and spake thus to them: That he had formerly dissuaded them from their own resolution, when they were ready to forsake Ishbosheth, and to join themselves to David; that, however, he now gave them leave so to do, if they had a mind to it, for they knew that God had appointed David to be king of all the Hebrews by Samuel the prophet; and had foretold that he should punish the Philistines, and overcome them, and bring them under. Now when the elders and rulers heard this, and understood that Abner was come over to those sentiments about the public affairs which they were of before, they changed their measures, and came in to David. When these men had agreed to Abner's proposal, he called together the tribe of Benjamin, for all of that tribe were the guards of Ishbosheth's body, and he spake to them to the same purpose. And when he saw that they did not in the least oppose what he said, but resigned themselves up to his opinion, he took about twenty of his friends and came to David, in order to receive himself security upon oath from him; for we may justly esteem those things to be firmer which every one of us do by ourselves, than those which we do by another. He also gave him an account of what he had said to the rulers, and to the whole tribe of Benjamin; and when David had received him in a courteous manner, and had treated him with great hospitality for many days, Abner, when he was dismissed, desired him to bring the multitude with him, that he might deliver up the government to him, when David himself was present, and a spectator of what was done.