I have been asked to show the tradition of the Church Fathers as the infallible source of truth outside of the Scriptures. So I have compiled a lengthy list of quotes that demonstrate this tradition consisted of a living Church ruled by Apostolic successors, was to be believed and obeyed as if it was the voice of God itself, contained truth not found in Scripture but harmonious with it, and that Scriptures cannot be understood apart from this tradition. I would encourage everyone to read the complete works or at least chapters in the works pertaining to tradition, heretics, and Scriptures, especially Irenaeus’s Against Heresies and Tertullian’s The Prescription Against Heretics. Catholic teachings are not only consistent with the view of tradition as seen below, but are consistent with the view of Scripture as seen in Holy Scripture: The Ground and Pillar of Our Faith Volume III. Although the sola scriptura may be consistent with the latter, it is decidedly not compatible with these views of tradition.
The following quotes define the tradition of which the Church Fathers speak as being the living Church, which transmitted Apostolic tradition through Apostolic succession. They assert this tradition as something to be obeyed as if you are obeying Christ himself.
Our Lord, whose precepts and admonitions we ought to observe, describing the honour of a bishop and the order of His Church, speaks in the Gospel, and says to Peter: I say unto you, That you are Peter, and upon this rock will I build my Church; and the gates of hell shall not prevail against it. And I will give unto you the keys of the kingdom of heaven: and whatsoever you shall bind on earth shall be bound in heaven: and whatsoever you shall loose on earth shall be loosed in heaven. Thence, through the changes of times and successions, the ordering of bishops and the plan of the Church flow onwards; so that the Church is founded upon the bishops, and every act of the Church is controlled by these same rulers. Since this, then, is founded on the divine law, I marvel that some, with daring temerity, have chosen to write to me as if they wrote in the name of the Church; when the Church is established in the bishop and the clergy, and all who stand fast in the faith.
[Cyprian, Letters, No. 33]
It is within the power of all, therefore, in every Church, who may wish to see the truth, to contemplate clearly the tradition of the apostles manifested throughout the whole world; and we are in a position to reckon up those who were by the apostles instituted bishops in the Churches, and [to demonstrate] the succession of these men to our own times; those who neither taught nor knew of anything like what these [heretics] rave about. For if the apostles had known hidden mysteries, which they were in the habit of imparting to the perfect apart and privily from the rest, they would have delivered them especially to those to whom they were also committing the Churches themselves.
[Irenaeus, Against Heresies, Book 3, Ch. 3]
Wherefore it is incumbent to obey the presbyters who are in the Church—those who, as I have shown, possess the succession from the apostles; those who, together with the succession of the episcopate, have received the certain gift of truth, according to the good pleasure of the Father. But [it is also incumbent] to hold in suspicion others who depart from the primitive succession, and assemble themselves together in any place whatsoever, [looking upon them] either as heretics of perverse minds, or as schismatics puffed up and self-pleasing, or again as hypocrites, acting thus for the sake of lucre and vainglory. For all these have fallen from the truth.
[Irenaeus, Against Heresies, Book 4, Ch. 26]
In the same way all should respect the deacons as they would Jesus Christ, just as they respect the bishop as representing the Father and the priests as the council of God and the college of the Apostles. Apart from these there is nothing that can be called a Church.
[Ignatius of Antioch, Letter to the Trallians, Ch. 2]
Let all follow the bishop as Jesus Christ did the Father, and the priests, as you would the Apostles. Reverence the deacons as you would the command of God. Apart from the bishop, let no one perform any of the functions that pertain to the Church. Let that Eucharist be held valid which is offered by the bishop or by one to whom the bishop has committed this charge. Wherever the bishop appears, there let the people be; as wherever Jesus Christ is, there is the Catholic Church. It is not lawful to baptize or give communion without the consent of the bishop. On the other hand, whatever has his approval is pleasing to God. Thus, whatever is done will be safe and valid.
[Ignatius of Antioch, Letter to the Smyrnaeans, Ch. 8]
The following shows that the Church Fathers indeed believed truth was transmitted through tradition, even truth beyond that found in Scripture and in every practice that was handed down through the succession of the apostles.
Therefore it is the Catholic Church alone which retains true worship. This is the fountain of truth, this is the abode of faith, this is the temple of God; into which if anyone shall not enter, or from which if any shall go out, he is estranged from the hope of life and eternal salvation.
[Lactantius, The Divine Institutes, Book 4, Ch. 30]
Since therefore we have such proofs, it is not necessary to seek the truth among others which it is easy to obtain from the Church; since the apostles, like a rich man [depositing his money] in a bank, lodged in her hands most copiously all things pertaining to the truth: so that every man, whosoever will, can draw from her the water of life. Revelation 22:17 For she is the entrance to life; all others are thieves and robbers. On this account are we bound to avoid them, but to make choice of the thing pertaining to the Church with the utmost diligence, and to lay hold of the tradition of the truth. For how stands the case? Suppose there arise a dispute relative to some important question among us, should we not have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary, [in that case,] to follow the course of the tradition which they handed down to those to whom they did commit the Churches?
[Irenaeus, Against Heresies, Book 3, Ch. 4]
I desire you therefore, in the first place, to hold fast this as the fundamental principle in the present discussion, that our Lord Jesus Christ has appointed to us a light yoke and an easy burden, as He declares in the Gospel: Matthew 11:30 in accordance with which He has bound His people under the new dispensation together in fellowship by sacraments, which are in number very few, in observance most easy, and in significance most excellent, as baptism solemnized in the name of the Trinity, the communion of His body and blood, and such other things as are prescribed in the canonical Scriptures, with the exception of those enactments which were a yoke of bondage to God’s ancient people, suited to their state of heart and to the times of the prophets, and which are found in the five books of Moses. As to those other things which we hold on the authority, not of Scripture, but of tradition, and which are observed throughout the whole world, it may be understood that they are held as approved and instituted either by the apostles themselves, or by plenary Councils, whose authority in the Church is most useful.
[Augustine, Letters, No. 54]
Here is an amusing and sarcastic exasperated exposition of Tertullian against heretics believing that they found the truth after error had been believed for an interval. It shows that tradition was used to determine truth, since truth was more likely transmitted closer to the Apostles time rather than later.
In whatever manner error came, it reigned of course only as long as there was an absence of heresies? Truth had to wait for certain Marcionites and Valentinians to set it free. During the interval the gospel was wrongly preached; men wrongly believed;… Else, if not wrongly done, and to no purpose, how comes it to pass that the things of God were on their course before it was known to what God they belonged? that there were Christians before Christ was found? that there were heresies before true doctrine? Not so; for in all cases truth precedes its copy, the likeness succeeds the reality.
[Tertullian, The Prescription Against Heretics, Ch. 29]
These quotes find the Church Fathers believed this tradition to be consistently and trust worthily transmitted through the Church. They are expounding the certainty of truth in tradition, that it will not go astray, and that we as Christians should trust it. In effect, they describe what may be seen as infallible Apostolic tradition.
From this, therefore, do we draw up our rule. Since the Lord Jesus Christ sent the apostles to preach, (our rule is) that no others ought to be received as preachers than those whom Christ appointed; for no man knows the Father save the Son, and he to whomsoever the Son will reveal Him. Matthew 11:27 Nor does the Son seem to have revealed Him to any other than the apostles, whom He sent forth to preach— that, of course, which He revealed to them. Now, what that was which they preached— in other words, what it was which Christ revealed to them— can, as I must here likewise prescribe, properly be proved in no other way than by those very churches which the apostles founded in person, by declaring the gospel to them directly themselves, both vivâ voce, as the phrase is, and subsequently by their epistles. If, then, these things are so, it is in the same degree manifest that all doctrine which agrees with the apostolic churches— those moulds and original sources of the faith must be reckoned for truth, as undoubtedly containing that which the (said) churches received from the apostles, the apostles from Christ, Christ from God. Whereas all doctrine must be prejudged as false which savours of contrariety to the truth of the churches and apostles of Christ and God. It remains, then, that we demonstrate whether this doctrine of ours, of which we have now given the rule, has its origin in the tradition of the apostles, and whether all other doctrines do not ipso facto proceed from falsehood. We hold communion with the apostolic churches because our doctrine is in no respect different from theirs. This is our witness of truth.
[Tertullian, The Prescription Against Heretics, Ch. 21]
Grant, then, that all have erred; that the apostle was mistaken in giving his testimony; that the Holy Ghost had no such respect to any one (church) as to lead it into truth, although sent with this view by Christ, John 14:26 and for this asked of the Father that He might be the teacher of truth; John 15:26 grant, also, that He, the Steward of God, the Vicar of Christ, neglected His office, permitting the churches for a time to understand differently, (and) to believe differently, what He Himself was preaching by the apostles,— is it likely that so many churches, and they so great, should have gone astray into one and the same faith? No casualty distributed among many men issues in one and the same result. Error of doctrine in the churches must necessarily have produced various issues. When, however, that which is deposited among many is found to be one and the same, it is not the result of error, but of tradition. Can any one, then, be reckless enough to say that they were in error who handed on the tradition?
[Tertullian, The Prescription Against Heretics, Ch. 28]
But [it has, on the other hand, been shown], that the preaching of the Church is everywhere consistent, and continues in an even course, and receives testimony from the prophets, the apostles, and all the disciples— as I have proved— through [those in] the beginning, the middle, and the end, and through the entire dispensation of God, and that well-grounded system which tends to man’s salvation, namely, our faith; which, having been received from the Church, we do preserve, and which always, by the Spirit of God, renewing its youth, as if it were some precious deposit in an excellent vessel, causes the vessel itself containing it to renew its youth also.
[Irenaeus, Against Heresies, Book 3, Ch. 24]
Now all these [heretics] are of much later date than the bishops to whom the apostles committed the Churches; which fact I have in the third book taken all pains to demonstrate. It follows, then, as a matter of course, that these heretics aforementioned, since they are blind to the truth, and deviate from the [right] way, will walk in various roads; and therefore the footsteps of their doctrine are scattered here and there without agreement or connection. But the path of those belonging to the Church circumscribes the whole world, as possessing the sure tradition from the apostles, and gives unto us to see that the faith of all is one and the same, since all receive one and the same God the Father, and believe in the same dispensation regarding the incarnation of the Son of God, and are cognizant of the same gift of the Spirit, and are conversant with the same commandments, and preserve the same form of ecclesiastical constitution, and expect the same advent of the Lord, and await the same salvation of the complete man, that is, of the soul and body. And undoubtedly the preaching of the Church is true and steadfast, in which one and the same way of salvation is shown throughout the whole world.
[Irenaeus, Against Heresies, Book 5, Ch. 20]
These quotes shows the relationship between Scripture and tradition as seen by Tertullian. It seems to be the same as the relationship described in the modern Catholic Church. Not only are they harmonious, transmitting the same truth of salvation, but also Scripture is lame without the true rule of faith to interpret it. It’s interesting that when there was dispute in tradition, many of the Church Fathers (like Irenaeus in Against Heresies) resorted to the Scriptures as a common accepted rule of faith, but Tertullian rejected this method on the grounds that people with different traditions would have different interpretations of Scripture.
Our appeal, therefore, must not be made to the Scriptures… “With whom lies that very faith to which the Scriptures belong. From what and through whom, and when, and to whom, has been handed down that rule, by which men become Christians?” For wherever it shall be manifest that the true Christian rule and faith shall be, there will likewise be the true Scriptures and expositions thereof, and all the Christian traditions.
[Tertullian, The Prescription Against Heretics, Ch. 19]
Since this is the case, in order that the truth may be adjudged to belong to us, as many as walk according to the rule, which the church has handed down from the apostles, the apostles from Christ, and Christ from God, the reason of our position is clear, when it determines that heretics ought not to be allowed to challenge an appeal to the Scriptures, since we, without the Scriptures, prove that they have nothing to do with the Scriptures. For as they are heretics, they cannot be true Christians, because it is not from Christ that they get that which they pursue of their own mere choice, and from the pursuit incur and admit the name of heretics. Thus, not being Christians, they have acquired no right to the Christian Scriptures;
[Tertullian, The Prescription Against Heretics, Ch. 37]
Where diversity of doctrine is found, there, then, must the corruption both of the Scriptures and the expositions thereof be regarded as existing… What we are ourselves, that also the Scriptures are (and have been) from the beginning. Of them we have our being, before there was any other way, before they were interpolated by you… One man perverts the Scriptures with his hand, another their meaning by his exposition.
[Tertullian, The Prescription Against Heretics, Ch. 38]