Martin Luther on the Church Fathers:
"The fathers did not want to have anyone believe them if they did not adduce clear Scripture; and the papists do an injustice to the fathers by wanting people to observe all their statements. Nor are they thereby seeking the honor of the fathers, but their own tyranny, that they may lead us out of Scripture, obscure faith, hatch out their own ideas, and become our idols. We should note this rule well.
For thus says St. Augustine, lib. 3. Trin. in prologo: I want to have such readers for my books as I am when I read the books of others: free and unfettered. Again he says, Epist. 8. ad Hieronymum: I do not suppose that you want people to consider your books as books of the prophets and apostles, for I believe that only Holy Scripture does not err. When I read the other books, I do not believe anything to be true just because they have said so; I believe it only if they prove it with clear reasons or from Holy Scripture. Look! Note this well: Augustine wants Scripture in his own and all other books.
Likewise, when St. Jerome relates the opinion of many of his predecessors, he passes this judgment: This is, however, not grounded in Scripture; therefore it is spurned just as readily as it is accepted. Look! Let whoever he may be say what he pleases; if he does not produce proof from Scripture, then you should say: It is spurned just as readily as it is accepted.
St. Hilary says likewise, lib. 2. Trin.: He is the best teacher who does not bring his opinion into the Scripture but brings it out of the Scripture. Likewise at another place: It is not fair to teach anything beyond the limits set by Scripture. Whoever presumes to do so certainly does not understand what he is teaching; or those who hear him do not understand it."
Source: Luther's comments on Psalm 37:40 (W 8, 238 f—E 39, 134f—SL 5, 336 f) from Ewald Plass (ed.), What Luther Says Vol. 1 (St Louis: Concordia Publishing House, 1959) 311.