Flavius Josephus,
Antiquities of the Jews
“ How Helena The Queen Of Adiabene And Her Son Izates, Embraced The Jewish Religion; And How Helena Supplied The Poor With Corn, When There Was A Great Famine At Jerusalem. 1. About this time it was that Helena, queen of Adiabene, and her son Izates, changed their course of life, and embraced the Jewish customs, and this on the occasion following: Monobazus, the king of Adiabene, who had also the name of Bazeus, fell in love with his sister Helena, and took her to be his wife, and begat her with child. ”
