Hagar and Ishmael are sent away

Now you, brothers, like Isaac, are children of promise. At that time, however, the son born by the flesh persecuted the son born by the Spirit. It is the same now. But what does the Scripture say? “Expel the slave woman and her son, for the slave woman’s son will never share in the inheritance with the free woman’s son.”

By faith Abraham, when he was tested, offered up Isaac on the altar. He who had received the promises was ready to offer his one and only son, even though God had said to him, “Through Isaac your offspring will be reckoned.” Abraham reasoned that God could raise the dead, and in a sense, he did receive Isaac back from death.

It is not as though God’s word has failed. For not all who are descended from Israel are Israel. Nor because they are Abraham’s descendants are they all his children. On the contrary, “Through Isaac your offspring will be reckoned.” So it is not the children of the flesh who are God’s children, but it is the children of the promise who are regarded as offspring. For this is what the promise stated: “At the appointed time I will return, and Sarah will have a son.”