Very often, those of us who believe in Salvation by faith alone are accused of believing a doctrine which did not exist until the time of the Reformation, when Martin Luther (1483-1546 AD) and John Calvin (1509-1564 AD) taught such a doctrine explicitly, and garnered large followings in Europe.
Therefore, we are told that such a doctrine, unknown to historical Christianity, could not possibly be true. How could a 16th century invention be true?
To begin, before getting into Church history, there are three considerations which need to be raised to attention.
Firstly, any doctrine - no matter how old, or how widely-held - must be tested rigorously against the inspired Scripture. We know that there were false prophets, teaching false doctrine amongst believers, from the very beginning, even while the New Testament itself was being written (John 21:21-23, Acts 20:28-31: 2 Corinthians 2:17, Galatians 1:6-7: 2 Peter 3:16, Revelation 2:15). The New Testament records the Apostle Paul being forsaken by churches that he helped found (2 Timothy 1:15), and the Apostle John being rejected from a congregation (3 John 1:9-10).
Therefore, age cannot be the rule by which we determine truth. There has always been heresy. Neither can popularity be used to determine truth. Jesus Christ specifically said that the way is narrow (Matthew 7:13-14), and the Apostle Peter warned that "many" would follow false prophets (2 Peter 2:1-2). The sole infallible standard has to be the inspired Scripture.
Secondly, Scripture has always been read out loud in churches. And, the Scripture teaches Salvation by faith alone. The number of people who heard Ephesians 2:8-9, or John 3:16 read aloud, and simply believed it, is doubtless to be large. Such people were born again, even if they only believed in Christ alone for a moment, in spite of their church's teachings. The same is true today.
Thirdly, it is ignorant to the point of foolishness to believe that we have even 1% of Church history. Most of the millions of sermons preached since Jesus's ascension disappeared from the historical record the same day that they were preached. For every epistle that we have from early Christians, we can assume that many thousands were written and discarded, either deliberately, or by the passage of time and circumstances.
It takes extremely favorable circumstances to have one's writings preserved for even 100 years after their death, in an age where writing supplies were expensive, and there was no internet or printing press. Unless they have a dedicated following, who manage to copy and distribute their teachings, unaltered, for hundreds of years, whatever they produce will be lost to history. This is especially the case if they are in the theological minority, and their theological opponents have political power. So, we must keep in mind, when studying Church history, that we only have access to a small part of it.
However, that being said, it is only ignorance or deceptiveness that would lead someone to state that the doctrine of Salvation by faith alone was an invention of the Reformation. It has witnesses throughout history, from the very beginning. And, though it has always been a persecuted, minority position - therefore appearing mostly in polemics attacking it, and those who believe it - it has nonetheless always existed, and been believed by faithful followers of Christ.
The first witness, outside of the New Testament, to the doctrine of Salvation by faith alone, can be found in the First Epistle of Clement to the Corinthians, most commonly dated to 96 AD:
First Clement 32:3-4 (96 AD)
3 They all therefore were glorified and magnified, not through themselves or their own works or the righteous doing which they wrought, but through His will.
4 And so we, having been called through His will in Christ Jesus, are not justified through ourselves or through our own wisdom or understanding or piety or works which we wrought in holiness of heart, but through faith, whereby the Almighty God justified all men that have been from the beginning; to whom be the glory for ever and ever. Amen.
Above is not only a testament to justification by faith, but justification by faith to the explicit exclusion of "works which we wrought in holiness of heart" - that is, good works. That is exactly our profession, and it is over 1,300 years before Luther or Calvin were even born, and hundreds of years before the formation of the Roman Catholic Church.
Gaius Marius Victorinus (291-365 AD) was an early Roman convert from Platonism to Christianity. He wrote a Latin commentary on some of the Pauline Epistles, which contains many clear witnesses to an understanding of the freeness of Salvation:
Victorinus (291-365 AD) - Commentary on Galatians, 2:16
We Jews, he says - that is, you and I, Peter, and the others - we who are sinners, however, are not from the Gentiles; rather, we are Jews. To be sure, we do maintain faith in Christ. What precisely is our reason, since we were Jews? Obviously, because we know that people are not justified based on works of the Law but are justified through faith, the faith in Jesus Christ. So since we knew this, says Paul, we have come to believe in Christ Jesus, and we believe in order that we might be justified based on faith, not works of the Law, seeing that no flesh - that is, the human being who is in flesh - is justified based on works of the Law.
So knowing this, if we have believed that justification comes about through faith, we are surely going astray if we now return to Judaism, from which we passed over to be justified based not on works but faith, and faith in Christ. For faith itself alone grants justification and sanctification. Thus any flesh whatsoever - Jews or those from the Gentiles - is justified on the basis of faith, not works or observance of the Jewish Law.
Victorinus (291-365 AD) - Commentary on Galatians, 3:2
So when I preached the gospel to you, you received the Spirit based on hearing of faith, therefore it was not based on works of the Law. And if it was not based on works of the Law, why are you now adding a Jewish teaching, such that you would believe you will receive the Spirit, know about God, and hope in God based on works of the Law? Why do this, when you already received the Spirit based on hearing of faith - that is, because you heard that faith in Christ ought to be pursued? Because if it is based on hearing, it is now contrary to faith when you believe you will receive the Spirit on the basis of works of the Law, because by faith alone in Christ the Spirit is given, and has been given, to you.
Victorinus (291-365 AD) - Commentary on Galatians, 3:7
Therefore it is understood that those who stand on the basis of faith are the children of Abraham (3:7). To the seed of Abraham have been promised many things. Now, Abraham himself was found acceptable, as regards justice, based on his faith. All of those who stand on the basis of faith, then, are among the children of Abraham, as I have often pointed out. The entire Mystery, which was enacted by our Lord Jesus Christ, requires faith alone.
Victorinus (291-365 AD) - Commentary on Galatians, 3:22
But Scripture has contained all things under sin, in order that the promise would be given to believers based on faith in Jesus Christ (3:22). This was accomplished, says Paul, through Moses: that he would indeed institute a law about sin; that the whole of Scripture would be about sin; and that all the things which are under sin be contained in it, so that what was promised would come about based on faith, and the inheritance be given to those who believe based on faith in Jesus Christ. So what is he doing, or what did he accomplish, by means of all this? That faith alone in Jesus Christ would suffice for our justification and liberation.
Victorinus (291-365 AD) - Commentary on Galatians, 3:26
For you are all sons of God by faith in Christ Jesus (3:26). For this is the inheritance: that we obtain eternal life. At that point we are sons of God. But where does this come from? By faith in Christ Jesus. This is when we have faith in Christ: in our believing in him, that he is the Son of God, that he himself saves us, and that he carried out that Mystery for our sake and did all those things in the gospel we have discussed.
Above, notice repeated statements that we are justified by "faith alone", which grants all of the benefits of "justification and liberation". And, in his comment on 3:26, notice a good definition of faith as believing in the work of Jesus Christ.
Another early reference to Salvation by faith alone can be seen in the works of Basil (330-379 AD):
Basil (330-379 AD) - Homily on Humility
This constitutes the highest dignity of man, this is his glory and greatness: truly to know what is great and to cleave to It, and to seek after glory from the Lord of glory. The Apostle tells us: 'He that glorieth may glory in the Lord,' saying: 'Christ was made for us wisdom of God, righteousness and sanctification and redemption; that, as it is written: He that glorieth may glory in the Lord.' Now, this is the perfect and consummate glory in God: not to exult in one's own righteousness, but, recognizing oneself as lacking true righteousness, to be justified by faith in Christ alone. Paul gloried in despising his own righteousness and in seeking after the righteousness by faith which is of God through Christ, that he might know Him and the power of His resurrection and the fellowship of His sufferings, being made conformable to His death, so as to attain to the resurrection from the dead.
The above demonstrates an understanding of simple justification by faith alone, and a reference to Philippians 3:9, which teaches the imputed righteousness of Jesus Christ to believers.
Next, John Chrysostom (347-407 AD), commenting on Romans 3:26, writes:
John Chrysostom (347-407 AD) - Homily 7 on Romans
So also is the declaring of His righteousness not only that He is Himself righteous, but that He does also make them that are filled with the putrefying sores of sin suddenly righteous. And it is to explain this, viz. what is "declaring", that he has added, "That He might be just, and the justifier of him which believes in Jesus". Doubt not then: for it is not of works, but of faith: and shun not the righteousness of God, for it is a blessing in two ways; because it is easy, and also open to all men.
Next, Ambrosiaster is the name given to an unknown author of a commentary on the Pauline Epistles, written between 366-384 AD. In his commentary on Romans, he is able to bring out the meaning of the text unambiguously, resulting in many good comments which demonstrate an understanding of justification by faith alone:
Ambrosiaster (366-384 AD) - Commentary on Romans, 3:24
"They are justified freely through his grace". They are justified freely, because they are sanctified by faith alone as a gift of God; they do nothing and render nothing in return.
Ambrosiaster (366-384 AD) - Commentary on Romans, 4:5-8
4:5 "But to one who does not work". That is, to one who is guilty of sins because he does not do what the law commands. "But believes in him who justifies the ungodly, his faith is reckoned as righteousness". The apostle says this because for the ungodly person who believes without works of the law - that is, a gentile - his faith in Christ is reckoned as righteousness, as was Abraham's faith.
How then do the Jews believe themselves to be justified through works of the law in accordance with Abraham's justification, when they see that Abraham was justified not by works of the law but by faith alone? Accordingly, there is no need for the law when an ungodly person is justified by faith alone before God. According to the plan of God's grace. The apostle says it was determined by God that when the law came to an end God's grace would require faith alone for salvation.
4:6 "The blessedness of the one to whom God reckons righteousness without works". David declares those people to be blessed whom God decreed would be justified before God by faith alone without toil and any observance.
4:7-8 "Blessed are those whose iniquities are forgiven and whose sins are covered. Blessed is the man against whom the Lord has not reckoned sin". Clearly, those whose iniquities are forgiven and whose sins are covered without toil or any work are blessed, since no works of repentance are demanded of them except that they believe.
In the days of Augustine, the number of those believing in Salvation by faith alone was sufficient enough to spur him to write a polemic against various forms of the doctrine, entitled "Faith and Works".
In it, he writes:
Augustine (354-430 AD) - Faith and Works, Chapter 14
Therefore, let us now see what must be torn away from the hearts of the God-fearing to prevent the loss of salvation through a treacherously false security, if, under the illusion that faith alone is sufficient for salvation, they neglect to live a good life and fail by good works to persevere in the way that leads to God.
Augustine (354-430 AD) - Faith and Works, Chapter 16
Those who argue in favor of the potency of faith alone for salvation use also the following text from the Apostle
The entire work contains many such quotes, and he attacks not only the doctrine, but those who held it, in various forms, while he was alive, 1,600 years ago.
Further, he mentions those with a belief in a form of Eternal Security - again in condemnation - in his megalithic work City of God, when discussing 1 Corinthians chapter 3:
Augustine (354-430 AD) - City of God, Book 21, Chapter 26
But, say they, the catholic Christians have Christ for a foundation, and they have not fallen away from union with Him, no matter how depraved a life they have built on this foundation, as wood, hay, stubble; and accordingly the well-directed faith by which Christ is their foundation will suffice to deliver them some time from the continuance of that fire, though it be with loss, since those things they have built on it shall be burned.
Once again, I understand that this mention is one of condemnation. That is exactly what we would expect to see in the case of a persecuted, minority doctrine, which I acknowledge Salvation by faith alone to be.
In the works of Caesarius of Arles, who has a preserved collection of 238 sermons, we read:
Caesarius of Arles (470-542 AD) - Sermon 186
Who is there who does not believe that Jesus is the Christ? Whoever does not live in the way which Christ commanded. For many say: I believe; and they think that faith alone without good works is sufficient.
Notice above, that even though he disagrees with Salvation by faith alone, he acknowledges that "many" during his time believed it. And, this was 1,000 years before the Reformation.
Vitally, it needs to be understood that these authors are not quoted to imply that they were consistent in their teaching of this doctrine. Even today, most who profess Salvation by faith alone may contradict themselves within the same sermon, or the very next day. Instead, the positive quotes are instances of glimmers of light, and the negative quotes are proofs that the doctrine, though often repudiated, was nonetheless in existence.
Salvation by faith alone is not new, because it is what the Apostles, and Jesus Christ taught. There is no other way to be justified before a perfect, holy God, and many throughout history understood that.