Clement of Alexandria (153-217?): The Stromata, or Miscellanies
For we have, as the source of teaching, the Lord, both by the prophets, the Gospels, and the blessed apostles, “in divers manners and at sundry times,” leading from the beginning of knowledge to the end. But if one should suppose that another origin was required, then no longer truly could an origin been preserved.
He, then, who himself believes the Scripture and voice of the Lord, which by the Lord acts to the benefiting of men, is rightly [regarded] faithful. Certainly we use it as a criterion in the discovery of things. What is subject to criticism is not believed till it is so subjected; so that what needs criticism cannot be a first principle. Therefore, as it is reasonable, grasping by faith the indemonstrable first principle, and receiving in abundance, from the first principle itself, demonstrations in reference to the first principle, we are by the voice of the Lord trained up to the knowledge of the truth.
For we may not give our adhesion to men on a bare statement by them, who might easily state the opposite. But if it is not enough merely to state the opinion, but if what is stated must be confirmed, we do not wait for the testimony of men, but we establish the matter that is in question by the voice of the Lord, which is the surest of all demonstrations, or rather is the only demonstration.
Philip Schaff, ed., The Ante-Nicene Fathers, vol. 2 (Grand Rapids: Eerdmans, 1989), 7.16, 551.