That assertion is not supported by evidence: the rule of Sola Scriptura is not taught in Scripture. The phrase --- an innovation in itself -- only became widespread (and "widespread" only in several countries in the northwestern corner of Europe) in the 16th-17th centuries.
Most of the Christian community in the rest of the world did not then, and does not now, accept it. We love "Scriptura" --- but the "Sola" part is a tradition of men.
So, can you back it up with evidence??
i should tell you right now that the references to the authority of Scripture are plentiful. Every Christian accepts that. Got it. For the sake of avoiding redundancy, there's no need to supply us with pages of cut-and-paste asserting that Scripture is authoritative. We know that.
But nobody has a problem with the "Scriptura" part. It's the "Sola" part.
That's the part I'm interested in.
Philip: "Thinkest thou that thou understandest what thou readest?"
The Ethiopian royal official: : "And how can I, unless some man show me?" (Acts 8:26-40)
Easily- the scriptures themselves are all the evidence I need. http://www.bible.ca/sola-scriptura-proof-texts.htm
The scriptures don’t allow for supplementation by “church traditions” over centuries. Don’t get hung up on the Latin term of convenience “Sola Scriptura.” The concept that the scriptures themselves are sufficient, and any doctrine contrary to them is to be rejected, was inherent in the scriptures from the beginning. The apostolic fathers also clearly taught that principle. http://www.bible.ca/sola-scriptura-anti-refuted-unscriptural.htm
But it’s not surprising that the political organization known as the RCC had to try to justify its existence somehow when it arose centuries after the church Christ had established. The only way to do that was to vary the apostles’ teaching. There are consequences to every decision.
And here’s a little more information on the validity of those traditions people cling to: http://www.bible.ca/sola-scriptura-tradition.htm
Let those who are willing to listen, listen.