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

[462] At this time the king gave order that the soldiers should go to supper, for it was late at night, while he went into a chamber to use the bath, for he was very weary; and here it was that he was in the greatest danger, which yet, by God's providence, he escaped; for as he was naked, and had but one servant that followed him, to be with him while he was bathing in an inner room, certain of the enemy, who were in their armor, and had fled thither, out of fear, were then in the place; and as he was bathing, the first of them came out with his naked sword drawn, and went out at the doors, and after him a second, and a third, armed in like manner, and were under such a consternation, that they did no hurt to the king, and thought themselves to have come off very well ill suffering no harm themselves in their getting out of the house. However, on the next day, he cut off the head of Pappus, for he was already slain, and sent it to Pheroras, as a punishment of what their brother had suffered by his means, for he was the man that slew him with his own hand.