Scripture is clear that the Lord Jesus Christ is the author [causer] of our Faith and the Finisher
Heb 12:2
2
Looking unto Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame, and is set down at the right hand of the throne of God.
That word author is the greek word archēgos and means:
the chief leader, prince
a) of Christ
2) one that takes the lead in any thing and thus affords an example, a predecessor in a matter, pioneer
3) the author
Now this word is made up of Two greek words one is archē and means:
beginning, origin
2) the person or thing that commences, the first person or thing in a series, the leader
3)
that by which anything begins to be, the origin, the active cause
4) the extremity of a thing
a) of the corners of a sail
5) the first place, principality, rule, magistracy
a) of angels and demons
Now Jesus Christ is the First active cause of our Faith. Now understand, the writer is not only speaking of believers under the New Covenant, but also of all the believers under the Old Covenant as outlined in Chapter 11 of Hebrews. Yes, He was the Author of their Faith even though He had not yet became incarnate, Yet He was still their Mediator and Surety before His Incarnation and so was the Author and Finisher of their Faith, the Captain of their Salvation !
But I said all that to bring up this, in order for Christ to be the Author of our Faith and to communicate it to us, there had to be a Union with Him prior to, as the branch must be united to the root before it can bring forth fruit
Jn 15:4-5
4 Abide in me, and I in you.
As the branch cannot bear fruit of itself,
except it abide in the vine; no more can ye, except ye abide in me.
5 I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing.