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

[16] But the doctrine of the Sadducees is this: That souls die with the bodies; nor do they regard the observation of any thing besides what the law enjoins them; for they think it an instance of virtue to dispute with those teachers of philosophy whom they frequent: but this doctrine is received but by a few, yet by those still of the greatest dignity. But they are able to do almost nothing of themselves; for when they become magistrates, as they are unwillingly and by force sometimes obliged to be, they addict themselves to the notions of the Pharisees, because the multitude would not otherwise bear them.