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

THIS fight proved to be on the same day whereon David was come back to Ziklag, after he had overcome the Amalekites. Now when he had been already two days at Ziklag, there came to him the man who slew Saul, which was the third day after the fight. He had escaped out of the battle which the Israelites had with the Philistines, and had his clothes rent, and ashes upon his head. And when he made his obeisance to David, he inquired of him whence he came. He replied, from the battle of the Israelites; and he informed him that the end of it was unfortunate, many ten thousands of the Israelites having been cut off, and Saul, together with his sons, slain. He also said that he could well give him this information, because he was present at the victory gained over the Hebrews, and was with the king when he fled. Nor did he deny that he had himself slain the king, when he was ready to be taken by the enemy, and he himself exhorted him to do it, because, when he was fallen on his sword, his great wounds had made him so weak that he was not able to kill himself. He also produced demonstrations that the king was slain, which were the golden bracelets that had been on the king's arms, and his crown, which he had taken away from Saul's dead body, and had brought them to him. So David having no longer any room to call in question the truth of what he said, but seeing most evident marks that Saul was dead, he rent his garments, and continued all that day with his companions in weeping and lamentation. This grief was augmented by the consideration of Jonathan; the son of Saul, who had been his most faithful friend, and the occasion of his own deliverance. He also demonstrated himself to have such great virtue, and such great kindness for Saul, as not only to take his death to heart, though he had been frequently in danger of losing his life by his means, but to punish him that slew him; for when David had said to him that he was become his own accuser, as the very man who had slain the king, and when he had understood that he was the son of an Amalekite, he commanded him to be slain. He also committed to writing some lamentations and funeral commendations of Saul and Jonathan, which have continued to my own age.