THE EPISTLE OF PAUL THE APOSTLE TO THE GALATIANS - Chapter 4 - Verse 22
Verse 22. For it is written. Ge 16, Ge 21.
Abraham had two sons. Ishmael and Isaac. Abraham subsequently had several sons by Keturah, after the death of Sarah, Ge 25:1-6. But the two sons by Hagar and Sarah were the most prominent, and the events of their lives furnished the particular illustration which Paul desired.
The one by a bond-maid. Ishmael, the son of Hagar. Hagar was an Egyptian slave, whom Sarah gave to Abraham in order that he might not be wholly without posterity, Ge 16:3.
The other by a free-woman. Isaac, the son of Sarah, Ge 21:1,2.