Thank you for the question on the father of all the faithful, “According to the New Testament book of Galatians, who is ‘The father of all the faithful?’”
As I read the Book of Galatians, the Apostle Paul said that Abraham is the man of faith.
Galatians 3 says this about Abraham as the father of the those who believe God and his promises, “So again I ask, does God give you his Spirit and work miracles among you by the works of the law, or by your believing what you heard? 6 So also Abraham “believed God, and it was credited to him as righteousness.”[c]
7 Understand, then, that those who have faith are children of Abraham. 8 Scripture foresaw that God would justify the Gentiles by faith, and announced the gospel in advance to Abraham: “All nations will be blessed through you.”[d] 9 So those who rely on faith are blessed along with Abraham, the man of faith” (NIV).
For one’s consideration, Abraham is known as the man of faith, not as the faithful man. The difference between a man of faith and a faithful man are as follows:
A. Ones who are loyal/faithful to God. One has to do with belief while the other has to do with action.
B. One has to do with trust while the other has to do with commitment/duty.
C. One has to do with dependence on God while the other has to do with dependence on self.
D. One has to do with belief while the other has to do with works.
E. One can be faithful in doing something and yet that action is without faith.
James says that faith without works is dead. The person who has faith will demonstrate that faith by his good works or being faithful in doing the commands of God. The Scripture commends Abraham for his faith in God. He is the model for everyone who comes to God must come by faith alone.
SUMMARY: Abraham is known for his belief in God and in his promises. He is the man of faith.