Of course, Christ quoted the Scriptures--generally if prophecies have been written down, and one is speaking of their fulfillment, one will cite the text, not the spoken version. And I quoted the Scriptures in this discussion (including a reference to Christ's own quotation of 'I have said ye are gods' from the Psalms)--conveniently ignored by my interlocutor.
Certainly what can be proven from the Scriptures, when 'rightly divided',
is true.
The problem with e-s's position is that he denies anything his own human reason, reading with the mind-set of a post-'Enlightenment' rationalist can't 'prove' from the Scriptures. This is absurd. All of the history of salvation since the Scriptures were written, much of which brings men to salvation in Christ, can't be 'proved' as from an axiom system from the Scriptures. One can't prove from Scripture that a GRU executioner was converted to Christ by the example of the New Martyr Lydia, but it's true, and the report of it comforted and inspired many persecuted by the Bolsheviks. One can't prove from Scripture that St. Seraphim of Sarov was transfigured in light, but it happened, and so forth.
Similarly, even Scripture tells us that not all of Christ's works were written down.
But in the face of this e-s denies the accounts of Joseph and Mary's life preserved by the Church simply because they aren't written in his Bible, and
worse, tars with the name of a small antinomian sect condemned in the Scriptures, almost all Christians who ever lived because we believe 'extra-Biblical' accounts.
The strain of protestant piety, which, having rejected various corrurptions of the Latin church (the sale of indulgences, bishops acting as temporal lords, and the like) throws out all of the patrimony of Christian Church 'from before the division of East and West' seizes the canon of Scripture (shortened, incidentally by Luther) as the only trustworthy thing is objectively self-contradictory. Having overthrown the authority of the Church and tradition, it lacks any real basis for establishing the authority of the Scriptures:
Why these Scriptures (which after all means 'writings', being the translation of the Greek 'graphe'), not others? Why not the 'Gospel of Judas'? or the 'Gospel of Thomas'?
In the end, the answer is, and must be, because the Church Christ founded (or made manifest) on the day of Pentecost in the descent of the Holy Spirit, judged certain books to be trustworthy, and not others. When the Scriptures were written, the list of the books we now regard as Scripture was not compiled, indeed most references to 'the Scriptures' in the New Testament manifestly refer only to the Scriptures already accepted by the Jews. (A matter of (horror!) *tradition*.)
Another thing you can't 'prove from Scripture', but which is nontheless true, is that we have a fairly complete account of the process by which the Church selected the canon of Scripture. And it took a long time. The first list of the New Testament Christians universally accept occurs in a letter of St. Athanasius the Great from the 4th century, all earlier listings either miss books or have extras. A local council at Carthage proposed the list now accepted by Orthodox and Latin Christians late in the 4th century, and it was only in the 7th century that there was clear explicit agreement to the Carthaginian decision by a general council (the canons of the Sixth Ecumenical Council explicitly ratify the acts of the Council of Carthage).
As I noted earlier: I'm coming to think Tertullian was right.