2 Tim 3:16
The question assumes that when Paul wrote 2 Tim 3:16 he was only referring to the Old Testament scriptures and whilst that is a view commonly presented it seems to ignore that Paul considered Luke's gospel to be scripture as well, consider 1 Tim 5:18:
1 Timothy 5:18 For the Scripture says, "You shall not muzzle an ox
while it treads out the grain," and, "The laborer is worthy of his
The phrase ""You shall not muzzle an ox while it treads out the grain," is quotation from Deut 25:4 however the phrase "The laborer is worthy of his wages." is a quote from Luke 10:71. In this verse verse Paul affirms that both these citations are 'scripture' hence we must conclude that Paul was aware that the process of inspiration was continuing and new books were been written. Hence it is logical to conclude that Paul had those books in mind as well when he later wrote 2 Tim 3:16.
Support for Paul quoting Luke 10:7 in 1 Tim 5:18
- The statement, ἄξιος ὁ ἐργάτης τοῦ μισθοῦ αὐτοῦ, is identical (except for the omission of the connective γάρ) to Jesus’ words in Lk. 10:7. Paul connects this statement to what precedes by a καί, which raises the question whether these words are, with those preceding, referred to by λέγει γὰρ ἡ γραφή and are thus regarded as a second citation of scripture. The practise of connecting quotations of scripture with a καί under a similar introductory formula is common practise amongst NT writers (ὁ γὰρ θεὸς εἶπεν, Mt. 15:4; Μωϋσῆς γὰρ εἶπεν, Mk. 7:10; γέγραπται γὰρ ἐν βίβλῳ ψαλμῶν, Acts 1:20; πρὸς δὲ τὸν υἱόν [λέγει understood from v. 7], Heb. 1:8; διότι περιέχει ἐν γραφῇ, 1 Pet. 2:6). 2 Pet. 2:22 connects two proverbs with καί under a single introductory formula, “according to the true proverb,” with the first from scripture and the second not. This pattern favours the fact that Paul is quoting two texts as scripture
- NA marginal cross references cite Luke 10:7 as the source of this quote.
- Comfort comments "The second quotation of scripture is nowhere to be found in the OT. Rather, it is a saying of Jesus from the gospels. As such, it is the only verse in the NT that ascribes scriptural status to the gospels. But which gospel does the quote come from? The wording in most manuscripts...is derived from Luke 10:7 but according to a few other witness (א*vid Clement) the wording is....a quotation Matt 10:101
Since ἄξιος κτλ. is evidently a quotation and is identical with Jesus’ words in Lk. 10:7, the source of these words would seem (most logically) to be Luke’s Gospel. Paul and Luke were friends, and were often together. Luke had been with Paul during the latter’s first Roman imprisonment(Col. 4:14; Philemon 24) and depending on one dating criteria Luke's gospel could have been in circulation for around 9 years when Paul writes to Timothy.
Paul is not alone in this understanding. Peter compares Paul's letters to the rest of scripture thereby including them as scripture:
2 Peter 3:15-16 and consider that the longsuffering of our Lord is salvation--
as also our beloved brother Paul, according to the wisdom given to
him, has written to you, 16 as also in all his epistles, speaking in
them of these things, in which are some things hard to understand,
which untaught and unstable people twist to their own destruction, as
they do also the rest of the Scriptures. [NJKV]
It is plain that both Paul and Peter (at least) understood that some of the material being produced by the apostles and their associates was on a par with the Old Testament canon.
1 P W Comfort, New testement text and translation commentray, Tyndale, 2008, p665