Who are sons of Abraham?

Galatians 3:5-14
New King James Version (NKJV)

5 Therefore He who supplies the Spirit to you and works miracles among you, does He do it by the works of the law, or by the hearing of faith?— 6 just as Abraham “believed God, and it was accounted to him for righteousness.” 7 Therefore know that only those who are of faith are sons of Abraham. 8 And the Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel to Abraham beforehand, saying, “In you all the nations shall be blessed.” 9 So then those who are of faith are blessed with believing Abraham.