John 16:12 – 13 – I still have many things to say to you, but you cannot bear them now. However, when He, the Spirit of truth, has come, He will guide you into all truth; for He will not speak on His own authority, but whatever He hears He will speak; and He will tell you things to come.
The Holy Spirit was present since the beginning but His role and ministry changed and became more predominant after the glorification of Jesus Christ. He was involved in creation, He anointed the Hebrew prophets with the Spirit of prophesy, and of course He was working through Jesus of Nazareth in the power of signs and wonders. For the common person either jew or gentile the Holy Spirit was just a mystery. That all began to change on the day of Pentecost as the anointing of the Holy Spirit fell on jews and gentiles alike, young and old, and male and female. The ministry of the Holy Spirit became front and center. This is how John Gill describes this.
“The Spirit of God in some sense had come, before the death of Christ; He had appeared in the creation of all things out of nothing, as a joint Creator with the Father and Son; He was come as a spirit of prophecy upon the inspired writers, and others; the Old Testament saints had received Him as a spirit of faith; He had been given to Christ as man, without measure, and the disciples had been partakers of His gifts and graces; but He was not come in so peculiar a manner as He afterwards did; as the promise of the Father, the glorifier of Christ, the comforter of His people, the spirit of truth, and the reprover of the world: there are reasons to be given, why the Spirit of God should not come in such a manner before…”
On the day of Pentecost Peter made all of this clear, the Holy Spirit would fall on all people who were thirsty for Him. Not only that, anyone and everyone could now become a mouthpiece for the Spirit of God. This was a most shocking development. The anointing was not just for the prophets or priests neither was it just for the jews. Everyone could now receive the Spirit and move in the power of the anointing. The Comforter had come and the world was dramatically changed.