The term “faith” is used in different senses in the New Testament. Frequently the word is employed subjectively, meaning it has to do with one’s personal belief — the faith that abides in the Christian’s heart.
At other times, “faith” is used in an objective sense. In such circumstances it stands for the gospel system — the body of doctrine to which one must submit.
In Galatians 1:23, Paul speaks of “the faith” (note the use of the definite article) which he preached. Since we learn elsewhere that the apostle preached “the gospel” (1 Corinthians 15:1), it is reasonable to conclude that “the faith” refers to the doctrine of the gospel. There are several New Testament references in which the expression is used in this fashion.
In Acts 6:7 Luke records that a great company of priests became obedient to “the faith,” which is equivalent to obeying the gospel (2 Thessalonians 1:8). The Christian is to contend earnestly for “the faith” (Jude 3), which is the same as defending the gospel (Philippians 1:16).
Thus, mark the phrase “the faith” in Galatians 1:23, and write: The gospel system; cf. Acts 6:7; Jude 3.