Galatians 4:22-23

4:22 For it is written that Abraham had two sons, one by the slave woman and the other by the free woman. 4:23 But one, the son by the slave woman, was born by natural descent, while the other, the son by the free woman, was born through the promise.

Galatians 5:10

5:10 I am confident in the Lord that you will accept no other view. But the one who is confusing you will pay the penalty, whoever he may be.