Therefore she said to Abraham, Cast out this bondwoman and her son, for the son of this bondwoman shall not be an heir with my son Isaac. [Gal. 4:28-31.]
They went out from our number, but they did not [really] belong to us; for if they had been of us, they would have remained with us. But [they withdrew] that it might be plain that they all are not of us.
For if the inheritance [of the promise depends on observing] the Law [as these false teachers would like you to believe], it no longer [depends] on the promise; however, God gave it to Abraham [as a free gift solely] by virtue of His promise.
But to the sons of his concubines [Hagar and Keturah] Abraham gave gifts, and while he was still living he sent them to the east country, away from Isaac his son [of promise].
But God said, Sarah your wife shall bear you a son indeed, and you shall call his name Isaac [laughter]; and I will establish My covenant or solemn pledge with him for an everlasting covenant and with his posterity after him.
And Gilead's wife also bore him sons, and when his wife's sons grew up, they thrust Jephthah out and said to him, You shall not have an inheritance in our father's house, for you are the son of another woman.