There is a distinction to be made between faith and the spirit of faith. The spirit of faith is faith in exercise. Faith sometimes is like a day in which there is no wind blowing. It is so calm, that there scarcely appears to be any air stirring to move a leaf. But after a time a gentle breeze comes and blows over the earth. Thus it is with faith and the spirit of faith. Faith in repose is like the calm air of a summer's day, when there is nothing moving or stirring; faith acting, faith in exercise, is like the same air in the gentle breeze which makes itself sensibly felt.
If God has given me faith, that faith is never lost out of my breast. If once a believer, I always am a believer; for if I could cease to believe, I should cease to be a child of God; I should lose salvation out of my heart, for I am saved by grace through faith. And yet there may be many times and seasons when I may not have much of the spirit of faith. Faith may be very inactive, I will not say stagnant, for that would almost imply death, but still, quiet, calm, sleeping like a bird with its head under its wing. But in due time there is a stirring, a movement, a gracious blowing of the Spirit: "Awake, O north wind, and come, O south; blow upon my garden" (Song Sol. 4:16). "Come from the four winds, O breath" (Ezek. 37:9).
This heavenly breath of the Holy Spirit acts upon faith, awakens it, revives and reanimates it, and draws it forth into lively operation. It thus becomes a spirit of faith, acting spiritually and energetically according to its measure. John was "in the Spirit on the Lord's day" (Rev. 1:10). He was not always in the Spirit by lively action, though he was never out of the Spirit by his extinction.
So faith is sometimes, so to speak, in the Spirit; and then its eyes are open, like the eyes of John, to see spiritually what he saw visibly, the Person of Christ, and its ear open to hear inwardly what he heard outwardly, the words of Christ.