Nothing mysterious was happening at Pentecost. The powers that came down from heaven had been foretold by the prophets and explained by Jesus in the flesh (John 15:26).
Peter begins his explanation by hearkening back to the old writings of Joel saying “This is that!” The events were part of the prophetic purpose of God to fulfill his promises with Israel.
Jesus said he did not come to destroy the old law but to fulfill it (Mat 5:17). Instead of changing the old instructions he amplifies them and instructs his disciples to do all that they are instructed by Moses seat (Matt 23:1-2).
After his resurrection Jesus explains how his ministry was all foretold in the old writings of the law and prophets.
“And beginning at Moses and all the prophets, he expounded unto them in all the scriptures the things concerning himself. ” – Luke 24:27
The new covenant which was destined to replace the old had been implied in the original covenant, in the thousands of year old promises, and by prophecies recorded for hundreds of years (Jer 31:31).
What was happening was anything but a surprise. God had spoken of it ‘since the world began’ (Acts 3:21).
However, something unprecedented happened on the road to Damascus. A man who had slaughtered Spirit-filled disciples and decried the teaching of the Messianic Jesus was offered free justification.
He was then given an unprecedented commission and a message unrevealed to any man before (Gal 1:11-12). He would be taught that God had ushered in a new period of grace and peace to all men whereby forgiveness would be offered by the cross and membership in a new creature.
In this dispensation Israel would be counted in unbelief along with the Gentiles and circumcision would not profit anyone.
“For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature. ” – Gal 6:15
Even the teaching of Jesus Christ became new. We are told we no longer know Christ as the the disciples knew him in the flesh as the prophesied Messiah. We know him as our Saviour!
“Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more.” – 2 Cor 5:16
Neither do preach salvation based on a covenant or through Israel but by God’s grace. The old things of the kingdom and Jew and Gentile distinction would be put aside and all things would become new. This revelation was called a mystery (Rom 16:25).
“Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.” – 2 Cor 5:17