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

[58] But as soon as Saul came into the house of his kinsman Abner, whom indeed he loved better than the rest of his relations, he was asked by him concerning his journey, and what accidents happened to him therein; and he concealed none of the other things from him, no, not his coming to Samuel the prophet, nor how he told him the asses were found; but he said nothing to him about the kingdom, and what belonged thereto, which he thought would procure him envy, and when such things are heard, they are not easily believed; nor did he think it prudent to tell those things to him, although he appeared very friendly to him, and one whom he loved above the rest of his relations, considering, I suppose, what human nature really is, that no one is a firm friend, neither among our intimates, nor of our kindred; nor do they preserve that kind disposition when God advances men to great prosperity, but they are still ill-natured and envious at those that are in eminent stations.