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

[34] Now, during the time Izates abode at Charax-Spasini, a certain Jewish merchant, whose name was Ananias, got among the women that belonged to the king, and taught them to worship God according to the Jewish religion. He, moreover, by their means, became known to Izates, and persuaded him, in like manner, to embrace that religion; he also, at the earnest entreaty of Izates, accompanied him when he was sent for by his father to come to Adiabene; it also happened that Helena, about the same time, was instructed by a certain other Jew and went over to them. But when Izates had taken the kingdom, and was come to Adiabene, and there saw his brethren and other kinsmen in bonds, he was displeased at it; and as he thought it an instance of impiety either to slay or imprison them, but still thought it a hazardous thing for to let them have their liberty, with the remembrance of the injuries that had been offered them, he sent some of them and their children for hostages to Rome, to Claudius Caesar, and sent the others to Artabanus, the king of Parthia, with the like intentions.