The bible, at the very least, contains documents which speak the truth concerning our faith in Jesus Christ, the gospel of God. It is abbreviated, yes we must admit. We do not have the resources to understand everything 100% as the original authors and recipients, but as historians, we can do our very best.
Christ did not commission of set script of literature for the authority of the Church just before ascending into heaven. However, you will notice that when the disciples met the risen Jesus, he was quite insistent that the events which had occurred were foretold in the Law of Moses and the Prophets. In fact, when the disciples doubted, instead of settling with the evidence of his physical body being alive again, dived right into the authoritative word of the Old Testament to bring to light the validity of such events.
Not only did Jesus say that his death, burial, and resurrection were already foretold in the infallible word of God in the Old Testament, but also his own words throughout his teaching ministry were foretold. And not only did the Old Testament foretell the coming suffering of the Messiah and the exalting glories that would follow, but that the actual dispensation of grace (Church-New Israel) of “preaching repentance for the remission of sins in His name” (Luke 24) was foretold. Therefore, you already have a worked base of looking into the Scriptures for not only the events of Jesus’ redemptive death and resurrection, but the ages that would follow in the form of “preaching the remission of sins”.
Moreover, the apostles were insistent, just as the Lord Jesus, that their doctrine is not from men, but from God, and it was not simply a Petrine dynastic structure that was enforced and assumed submission, no, no, no, the apostles themselves were equipped with miraculous signs and wonders, in conjunction with the evidence of the empty tomb, in conjunction with the Scriptures themselves. Why do we wonder that the first sermon of the Apostle Peter is not a claim to enthronment or some steward role under Christ the king, but that the Scripture has foretold the events that were happening.
Therefore, right from the very inception of the Church, you have many protestant elements going on. The Scriptures are prominent in the apostolic theology and doctrine (Acts 2). Hereafter, we read the Apostle Phillip and Paul, barnabas, and Silas, not excluding Apollos, defending their doctrine from the Law of Moses and the Prophets.
Therefore, the apostles themselves lived under the authority of the Law of Moses and the Prophets.
Yes, people needed someone to explain the old testament (see the Eunech in Acts 8), but others (Bereans) were themselves happy to find it themselves. This shows that it is not simply left to one man or group to be the final arbiters on what verses mean, but that in conjunction with this is the free available intellect of the human being to engage in the literature of the Old Testament to validate the apostolic claims. Surely, how can someone argue against this very principle?
Right through and through until the end of Luke’s account, Paul is holding up the Law of Moses and the Prophets to testify of Jesus and the Kingdom of God.
Therefore, it is theoretically possible for us to have the right doctrine of our era of grace from simply the Old Testament. This is something Paul was aware of, having told Timothy that the Old Testament was useful in everything pertaining to life and salvation. Such statements are extremely weakening to the additions which were to come some 1000 years later concerning the divine doctrines of Mary, the Lord’s mother, which no one was concerned with in Jerusalem at the Church’s inception.