The Secret History by Procopius

For soon Belisarius went off to war on Chosroes,8 and he took Photius with him; but Antonina remained behind, though this was contrary to her usual habit. She had always preferred to voyage wherever her husband went, lest he, being alone, come to his senses and, forgetting her enchantments, think of her for once as she deserved. But now, so that Theodosius might have free access to her, she planned once more how to rid herself permanently of Photius. She bribed some of Belisarius's guards to slander and insult her son at all times; while she, writing letters almost every day, denounced him, and thus set everything in motion against him. Compelled by all of this to counterplot against his mother, Photius got a witness to come from Constantinople with evidence of Theodosius's commerce with Antonina, took him to Belisarius, and commanded him to tell the whole story.

When Belisarius heard it, he became passionately angry, fell at Photius's feet, kissed them, and begged him to revenge one who had been so wronged by those who should least have treated him thus. "My dearest boy," he said, "your father, whoever he was, you have never known, for he left you at your mother's breast when the sands of his life were measured. Nor have you even benefited from his estate, since he was not over-blessed with wealth. But brought up by me, though I was only your stepfather, you have arrived at an age where it becomes you to avenge my wrongs. I, who have raised you to consular rank, and given you the opportunity of acquiring such riches, might call myself your father and mother and entire kindred, and I would be right, my son. For it is not by their kinship of blood, but by their friendly deeds that men are wont to measure their bonds to one another.