A beginner at Bible study can see that the popular doctrine of salvation by "faith only" is wrong. This expression is used but once in the New Testament --- when James writes: "Ye see then how that by works a man is justified, and not by faith only." (James 2:24)
Those who refuse to recognize the various ways in which the word "faith" is used in the N. T. are faced with stubborn contradictions (especially between the Roman letter and James) and must devise some ingenious quibbles to escape their dilemma.
The word "faith" is sometimes subjective, referring to the conscience. In such usage "of faith" assures sincerity, but does not necessarily prove truth. And in Jude 3, the word necessarily is used with reference to that which produces faith -- the evidence. But perhaps "faith" is most abused when we fail to recognize its application to the whole New Covenant. The oft-quoted "justification by faith" passages (Rom. 1:17 Ga1.3:11) point not to "faith only" but to a contrast system of faith (Christianity) with the system of law as manifested in Judaism.
A system of law demands perfect compliance; with reward on a basis of merit. "Cursed is everyone that continueth not in all things which are written in the book of the law to do them." (See Gal. 3:10-f) Since all sin, our only hope lies a system with provisions for forgiveness -- and that means Jesus Christ is our only hope.
Salvation is "not of works", i.e., we must not depend upon a system of merit, for we all sin. But we must put our trust (and here is faith) in Christ, who forgives. (Rom. 4:4-8) The Christian system is therefore a system of faith, and is characterized.
"Before faith came" means before the Christian system: "we were kept under the law" --- under .Judaism. The "children of God by faith" are those "baptized into Christ." (Gal. 3:23-f,)
In reality, one's faith in Christ is inadequate if it does not motivate "faithfulness." "This is the love of God, that we keep his commandments. (1 Jn. 5:3) Significantly, the original statement of "the just shall live by faith" (Heb. 2:4) refers to "faithfulness." (See ARV* footnotes.)
*American Revised Version translation (1901)
-Robert F. Turner; Plain Talk (Burnet, TX) Vol. 1, #6, June 1964, p.3 www.wordsfitlyspoken.org