According to the Talmud, Jethro together with Balaam and Job was consulted by Pharaoh as to the means for exterminating the children of Israel; and as he dissuaded Pharaoh from his design, he was recompensed in that his descendants, the Rechabites, sat with the Sanhedrin in the Temple (Talmud Sanhedrin.
It is further said (Exodus Rabba l.c.) that Jethro, having remarked that the worship of an idol was foolish, abandoned it [REF].