Toldos - Sheini
Do Not Disturb
Yitzchak settled in Gerar, but he copied his father's old trick and told the locals that Rivka was his sister. Unlike Sarah, Rivka did not end up getting abducted, but Avimelech, king of Gerar, saw Yitzchak treating Rivka in a most un-sibling-like fashion, so he knew that he had been deceived. (This was probably not the same Avimelech as in Avraham's day. "Avimelech" is a title for the position, like "Pharaoh.")
Avimelech chastised Yitzchak for saying Rivka was his sister, since one of the people could have taken Rivka, which they wouldn't do if she were known to be married. (Apparently they respected the institution of marriage if not a woman's right to choose her own spouse.) However, Yitzchak's fear for his own safety was justified, so Avimelech gave orders that neither Yitzchak nor Rivka were to be touched, on pain of death.