Q. Why did Abraham send all his sons away from Isaac?
The book of Genesis tells us that after Sarah died, “Abraham married another wife, named Keturah.” She bore him six sons. The book goes on to explain that “Abraham left everything he owned to Isaac. But while he was still living, he gave gifts to the sons of his concubines and sent them away from his son Isaac to the land of the east.” The plural word “concubines” refers both to Keturah and to Hagar, another wife of Abraham who was the mother of Ishmael.
So the reason why Abraham sent the other sons away seems to be that he wanted to make sure that Isaac indeed inherited his estate. He may have been concerned that after his death, the six sons of Keturah, whose mother would likely still have been living (since Keturah seems to have been younger than Abraham), might have banded together against Isaac, the son of a different mother who had died, to try to claim the inheritance for themselves.
The case of Jephthah presents a comparable, even though slightly different, example. He was the eldest son of a man named Gilead, though his mother was a prostitute. The book of Judges relates, “Gilead’s wife also bore him sons, and when they were grown up, they drove Jephthah away. ‘You are not going to get any inheritance in our family,’ they said, ‘because you are the son of another woman.'” Abraham may have been concerned that the same kind of thing would happen to Isaac, and so he sent the other sons to live in another place.
The Bible does not say whether Keturah’s sons actually would have tried to get the inheritance away from Isaac. It does not say whether Abraham sending them away was a good or a bad thing. So we have to come to some conclusion about that ourselves. In this post, “Who was Abraham’s second wife, Hagar or Keturah?” I say that Hagar (along with her son Ishmael) “is one of the figures in the Bible who is treated worst by the people who were supposed to be following and obeying God.” We might similarly wonder whether it was right for Abraham to remarry after Sarah’s death but then treat his second wife’s sons so unfavorably compared with his first wife’s son. We would probably not think that was suitable if someone did it today. So beyond the question of why Abraham sent the other sons away, we have the question of whether that was a proper thing for him to do. And we must come to some conclusion about that by reflecting on all the principles that the Bible teaches us.