Peter understood that the Scriptures came from God. He began the selection of a new apostle by appealing to the inspired Word. “Brothers’ the Scripture had to be fulfilled, which the Holy Spirit spoke beforehand by the mouth of David concerning Judas” (Acts 1:16). He continues to quote from the Psalms to show that another must be selected. Notice that Peter describes the Scripture as being through David but by the Holy Spirit. They were not merely the words of man, they are the words of God.
2 Peter 3:15-16 records some great information concerning the Scriptures. Peter there wrote, “And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, as he does in all his letters when he speaks in them of these matters. There are things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures.”
In that one passage we see that Paul’s writing were being collected and circulated. Peter was aware of Paul’s writings. He knew that Paul had written to the same audience he was addressing. He also understood “all his letters” were being circulated together. We also see that Paul’s writing were “according to the wisdom given him.” Surely, this is a description of God revealing the message to Paul. Finally, we see that Paul’s writing is described as being equal with “the other Scriptures.”
To use the word “Scriptures” (γραφὰς) to describe Paul’s writing was no small thing. The Exegetical Dictionary of the New Testament notes that “the word γραφή is nowhere used in the NT for non-biblical literature.” A similar phenomenon occurs in 1 Timothy 5:18, “For the Scripture says, ‘You shall not muzzle an ox when it treads out the grain,’ and, ‘The laborer deserves his wages.’” The first “Scripture” is found in Deuteronomy 25:4. But the second “Scripture” is not from the Old Testament. The words “the laborer deserves his wages” are the words of Jesus found in Luke 10:7. Both the Old and New Testament were viewed as Scripture—being from God.