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

[161] HEROD'S other affairs were now very prosperous, and he was not to be easily assaulted on any side. Yet did there come upon him a danger that would hazard his entire dominions, after Antony had been beaten at the battle of Actium by Caesar [Octarian]; for at that time both Herod's enemies and friends despaired of his affairs, for it was not probable that he would remain without punishment, who had showed so much friendship for Antony. So it happened that his friends despaired, and had no hopes of his escape; but for his enemies, they all outwardly appeared to be troubled at his case, but were privately very glad of it, as hoping to obtain a change for the better. As for Herod himself he saw that there was no one of royal dignity left but Hyrcanus, and therefore he thought it would be for his advantage not to suffer him to be an obstacle in his way any longer; for that in case he himself survived, and escaped the danger he was in, he thought it the safest way to put it out of the power of such a man to make any attempt against him, at such junctures of affairs, as was more worthy of the kingdom than himself; and in case he should be slain by Caesar, his envy prompted him to desire to slay him that would otherwise be king after him.