In John 16:12-13, Jesus tells the disciples "“I still have many things to say to you, but you cannot bear them now. However, when He, the Spirit of truth, has come, He will guide you into all truth; for He will not speak on His own authority, but whatever He hears He will speak; and He will tell you things to come." Many Catholics severely abuse this verse, claiming it refutes the Sufficiency of Scripture, and shows that the Church will forever be guided into new truths by the Holy Spirit. Scripture, they say, is not, nor has it ever been, enough. We need "Sacred tradition" to complete our faith.
Even reading the verse alone will show that this interpretation is wildly out of context. It says nothing of the sort. It does not say, either within the verse, or in the surrounding verses, or in the entire Bible, that there are any truths that would never be revealed in scripture, but rather to the mythical successors of the Apostles. In fact, it quite clearly says "you cannot bear them now" and "He will guide you into all truth". It seems, therefore, that Jesus was planning to send the Holy Spirit to the Apostles, specifically, to guide them into all truth.
But could they bear these truths at that time? Certainly not. First, consider Mark's account of the transfiguration: "Now as they came down from the mountain, He commanded them that they should tell no one the things they had seen, till the Son of Man had risen from the dead. So they kept this word to themselves, questioning what the rising from the dead meant." (Mark 9:9-10). Now, in the modern day, we know exactly what Jesus meant by rising from the dead. He meant He was going to die, and on the third day, the stone would roll away from His tomb and He would walk right back out. But this was apparently such a difficult concept for them that they questioned what it meant.
Peter had no such difficulty. In Matthew 16:21-23, we read "From that time Jesus began to show to His disciples that He must go to Jerusalem, and suffer many things from the elders and chief priests and scribes, and be killed, and be raised the third day. Then Peter took Him aside and began to rebuke Him, saying, “Far be it from You, Lord; this shall not happen to You!” But He turned and said to Peter, “Get behind Me, Satan! You are an offense to Me, for you are not mindful of the things of God, but the things of men.”" Clearly understanding that Jesus was saying He would die and rise again, Peter nevertheless could not bear this teaching, to the point where he rebuked Jesus for teaching it.
These two simple examples clearly show us that although the disciples were faithful, there was a lot for them to learn, and a lot had to happen before they were ready to receive even the most vital truths. For Christians living after the resurrection, it is unfathomable to ask "what did Jesus mean by rising from the dead?" And only a complete heretic would say actually, that never happened to Jesus. The death and resurrection of Christ are the cornerstones of our whole religion. Questioning or denying them is absurd. Yet the disciples did. This is what is meant by "you cannot bear them now".
But could they bear them later? Indeed so. The New Testament is flooded with truth that had not been revealed to the disciples at the point of John 16, by which point Jesus had not even been arrested (the arrest happens in chapter 18). So is it not remotely possible that Jesus fulfilled the promise of John 16:12-13 before the close of the New Testament?
Let's consult Jude: "Beloved, while I was very diligent to write to you concerning our common salvation, I found it necessary to write to you exhorting you to contend earnestly for the faith which was once for all delivered to the saints." (v3). This, right here, clearly tells us that we aren't expecting anything particularly new. Of course, there is the complicated question of how does this work if Revelation was written later? The simplest answer, if indeed we accept the standard authorship dates, is that Revelation doesn't really add anything new. It contains prophecy, and it "encourages" consistency, but even if you completely chopped Revelation out of the Bible, you wouldn't lose any doctrines. Since the faith is not affected by Revelation (and obviously isn't affected by Jude's own epistle), we can easily reconcile the revelation of Revelation with the fact that the truths the Apostles had been preaching for years were quite sufficient.
But by Jude's time, the Catholic Church had still not evolved. Most of Catholicism's unique doctrines had not even been conceptualised. There was no concept of Purgatory in Christianity at that time. There was no Papacy. There was no special class of priests. The perpetual virginity of Mary would have been an alien concept to the New Testament authors, given that two of them (James and Jude) wrote scripture. Indeed, the whole Catholic concept of "venerating" Mary is repugnant to scripture. These things aren't truths the disciples couldn't bear, but the Catholic Church would receive them from the Holy Spirit later on. They are lies, absorbed by the Catholic Church throughout history.
And so we see that while this verse is so commonly used as an attack on Sola Scriptura and a defence of Catholicism's non-Biblical traditions, to do this is nothing short of eisegesis. Jesus was not saying the Apostles could not bear His traditions yet, but the Holy Spirit would reveal them later. He was saying to men who could not yet accept that He was going to die and rise again that after His resurrection, He would guide them to all truth. By the time of Jude, we see that this promise has been fulfilled, even before the closing of the canon. Now that the canon has closed, and sadly the Apostles are no longer with us, we can safely rely on the word of God to make the man of God complete, and thoroughly equipped for every good work (2 Timothy 3:16-17). We have no need for the extra stuff Catholicism added over the centuries.