One of the most difficult lessons which we are called to learn, one however which is indispensable, if we would know the heights and depths of the religious life, is that of living by simple faith. God expects us, and has a right to expect us to leave ourselves and all our interests in his hands, in the full confidence, that he will do every thing which is right. And it is obviously the duty of every Christian, to correspond to this claim on the part of God, and to yield himself up, body and spirit, in the bonds of an everlasting covenant; fully believing that God will not desert him, neither in duty nor in temptation; and whether he is led in light or in darkness, with sensible manifestations and testimonies or without them, that all things will be well in the end, and will work together for his own good and for the divine glory. But too often this duty is not regarded. To live by faith, to lean upon the mere word of God without the supports of sight, is a very humbling way of living; and it is hard for the natural man and even for the partially sanctified man to receive it. Nature, so far as it exists in the heart, chooses another method, one more suited to itself, but less glorious to God. Some good Christians have exceedingly perplexed and injured themselves, for a considerable length of time, by attempting to maintain the inward life on the erroneous system of special signs, tokens, and testimonies, such as an audible voice, the application of some unknown passage of Scripture, the occurrence of some remarkable temporal event, the possession of a preconceived and specified state of joyous feeling, or something of the kind, which, in their ignorance or under the influence of remaining self-will, are earnestly sought from God, as the pledges and evidences of their acceptance. Such a system of living has scarcely any affinity, and perhaps none at all, with the true life of God in the soul. The Christian life, we repeat, is emphatically a LIFE OF FAITH; but to endeavor to live in the way, which has just been referred to, is evidently a deviation from the way of faith, and tends directly to strengthen the unspeakable evil of distrust in God.
From every thing of this kind, therefore, we must separate ourselves without hesitation, however painful the process may be. In the spirit of self-crucifixion, we must learn the great lesson of relying by simple belief on the mere declaration of God. And in doing this we need not fear. What need has the principle of inward faith of any sign or testimony additional to itself? Faith, whenever it is strong enough to be a true light within, will always bear its evidence in its own nature. It no more asks or requires exterior illumination, than the sun in the heavens asks for a taper to learn its own illuminated position. "He, that believeth on the Son of God, hath the witness in himself."
— edited from The Interior or Hidden Life (1844) Part 2, Chapter 10.