Wife–sister narratives in the Book of Genesis

There are three wife-sister narratives in Genesis, part of the Torah, all of which are strikingly similar. The narratives occur in Genesis 12, 20 and 26. At the core of each is the story of a Biblical Patriarch, who has come to be in the land of a powerful foreign overlord who misidentifies the Patriarch's wife as the Patriarch's sister, and consequently attempts to wed her himself. The overlord later finds out his error. Two of the three stories are similar in many other details, including the ruler's name, Abimelech.