Much or all of our OT was accepted as Scripture among Jews in Jesus’ day (Lk 24:44); by the end of the first century the consensus was final.
NT books were recognized as Scripture because they were: (a) written by an apostle or his associate; (b) widely circulated in the early church; (c) consistent with apostolic teachings and OT Scripture.
Many NT books were accepted as Scripture and were in wide circulation very early (Col 4:16; 1Th 5:27; 2Pt 3:15-16).
God brought the canon of Scripture together through the divine guidance of the Holy Spirit at work in God’s people.
Want more? Check out the Apologetics Study Bible for Students on page 1296 or visit ApologeticsBible.com.