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

[196] When God had thus resolved concerning the Sodomites, Abraham, as he sat by the oak of Mambre, at the door of his tent, saw three angels; and thinking them to be strangers, he rose up, and saluted them, and desired they would accept of an entertainment, and abide with him; to which, when they agreed, he ordered cakes of meal to be made presently; and when he had slain a calf, he roasted it, and brought it to them, as they sat under the oak. Now they made a show of eating; and besides, they asked him about his wife Sarah, where she was; and when he said she was within, they said they would come again hereafter, and find her become a mother. Upon which the woman laughed, and said that it was impossible she should bear children, since she was ninety years of age, and her husband was a hundred. Then they concealed themselves no longer, but declared that they were angels of God; and that one of them was sent to inform them about the child, and two of the overthrow of Sodom.