" Commenting on John 17:20, Calvin wrote, Woe to the Papists, whose faith is so far removed from this rule, that they are not ashamed to vomit out this horrid blasphemy, that there is nothing in Scripture but what is ambiguous, and may be turned in a variety of ways. The tradition of the Church is therefore their only authoritative guide to what they shall believe. But let us remember that the Son of God, who alone is competent to judge, does not approve of any other faith than that which is drawn from the doctrine of the apostles, and sure information of that doctrine will be found no where else than in their writings.1 "

― John Piper , The Supremacy of God in Preaching