Adam Clarke's Commentary on the Bible

Verse 8 (Galatians 3:8)

The Scripture, foreseeing - See the notes on Romans 4:3-16 ; (note). As God intended to justify the heathen through faith, he preached the Gospel that contains the grand display of the doctrine of salvation by faith, before, to Abraham, while he was in his heathen state; and thus he is called the father of believers: therefore it must refer to them who shall believe the same Gospel among the Gentiles; and, as the door of faith was open to all the Gentiles, consequently the promise was fulfilled: In thee shall all the nations of the earth be blessed.

- Adam Clarke's Commentary on the Bible