"But a most pernicious error widely prevails that Scripture has only so much weight as is conceded to it by the consent of the church. As if the eternal and inviolable truth of God depended upon the decision of men!"
"But such wranglers are neatly refuted by just one word of the apostle. He testifies that the church is 'built upon the foundation of the prophets and apostles' [Ephesians 2:20]. If the teaching of the prophets and apostles is the foundation, this must have had authority before the church began to exist. Groundless, too, is their subtle objection that, although the church took its beginning here, the writings to be attributed to the prophets and apostles nevertheless remain in doubt until decided by the church. For if the Christian church was from the beginning founded upon the writings of the prophets and the preaching of the apostles, wherever this doctrine is found, the acceptance of it — without which the church itself would never have existed — must certainly have preceded the church.
It is utterly vain, then, to pretend that the power of judging Scripture so lies with the church that its certainty depends upon churchly assent. Thus, while the church receives and gives its seal of approval to the Scriptures, it does not thereby render authentic what is otherwise doubtful or controversial. But because the church recognizes Scripture to be the truth of its own God, as a pious duty it unhesitatingly venerates Scripture. As to their question — How can we be assured that this has sprung from God unless we have recourse to the decree of the church? —it is as if someone asked: Whence will we learn to distinguish light from darkness, white from black, sweet from bitter? Indeed, Scripture exhibits fully as clear evidence of its own truth as white and black things do of their color, or sweet and bitter things do of their taste."
Source: Calvin's Institutes I.7.1-2