1Thess 5:21

“"For every one that useth milk is unskilful in the word of righteousness; for he is a babe," and not yet acquainted with the word, according to which he has believed and works, and not able to give a reason in himself. "Prove all things," the apostle says, "and hold fast that which is good," speaking to spiritual men, who judge what is said according to truth, whether it seems or truly holds by the truth.”

“And therefore "heresies must needs be in order that they which are approved might be made manifest," both those who remained stedfast under persecution, and those who did not wander out of their way into heresy. For the apostle does not mean that those persons should be deemed approved who exchange their creed for heresy; although they contrariously interpret his words to their own side, when he says in another passage, "Prove all things; hold fast that which is good; " as if, after proving all things amiss, one might not through error make a determined choice of some evil thing.”

“Herein consists the defence of our opinion, in accordance with Scripture, in accordance with Nature, in accordance with Discipline. Scripture founds the law; Nature joins to attest it; Discipline exacts it. Which of these (three) does a custom founded on (mere) opinion appear in behalf of? or what is the colour of the opposite view? God's is Scripture; God's is Nature; God's is Discipline. Whatever is contrary to these is not God's. If Scripture is uncertain, Nature is manifest; and concerning Nature's testimony Scripture cannot be uncertain. If there is a doubt about Nature, Discipline points out what is more sanctioned by God. For nothing is to Him dearer than humility; nothing more acceptable than modesty; nothing more offensive than "glory" and the study of men-pleasing. Let that, accordingly, be to you Scripture, and Nature, and Discipline, which you shall find to have been sanctioned by God; just as you are bidden to "examine all things, and diligently follow whatever is better."”

“I indeed gave attention to reading the books and carefully studying the traditions of heretics, to the extent indeed of corrupting my soul with their execrable opinions; yet receiving from them this advantage, that I could refute them in my own mind, and detested them more heartily than ever. And when a certain brother of the order of presbyters sought to deter me, and feared lest I should be involved in the same wicked filthiness, because he said that my mind would be contaminated, and indeed with truth, as I myself perceived, I was strengthened by a vision that was sent me from God. And a word spoken to me, expressly commanded me, saying, Read everything which shall come into thy hands, for thou art fit to do so, who correctest and provest each one; and from them to thee first of all has appeared the cause and the occasion of believing. I received this vision as being what was in accordance with the apostolic word, which thus urges all who are endowed with greater virtue, "Be ye skilful money-changers."”

“Then he says, but test everything, he shows how they ought to behave towards everything; and one piece of advice is that they should make use of discretion in all matters. "Your spiritual worship" (Rom. 12:1). In this matter there should be a careful examination, the election of the good, and the rejection of the evil. In treating the first point Paul says, do not despise prophesying, nevertheless, test everything, that is, those which are dubious; for matters that are evident do not require examination. "Do not believe every spirit" (1 Jn. 4:1). "Does not the ear try words?" (Job 12:11). Concerning the second, he says, hold fast what is good. "For a good purpose it is always good to be made much of" (Gal. 4:18).”