Some Scripture-Digging Tips
Look at the linguistics.
Which words do you feel the Holy Spirit pulling you toward? Dig into them to see what you can find to better understand this passage.
Pair the passages.
Read this section of Galatians alongside Genesis 16 and Genesis 21:1-14. How does the truth of one give further insight into the others?
The Technicalities
Not quite ready to drop his point about Isaac and Ishmael, Paul returns again to their respective stories in Genesis.