Red lines – Mikketz
Joseph as an Egyptian official told the Israelites (who actually were his brothers) that he had a special cup which he used for divination (Gen. 44:15).
The Midrash B’reshit Rabbah 92:5 tells us that by means of this cup he pretended to work out the age order of his brothers, though of course he already knew this from his youth and could not yet reveal who he was.
Yet the Torah is adamant that magical or semi-magical practices were not permitted to Jews (Deut. 18:12).
The Targum Onkelos re-interprets what Joseph told his brothers by suggesting that court officials carried out extensive tests – and outsiders thought it was all magic. Probably what was going on was that Joseph had to be seen as acting as a high Egyptian official would, but it was all an act.
Being a Jew in a non-Jewish environment was never easy; the danger is that after a while the play-acting becomes natural. There must always be red lines which a Jew must not cross.