Matthew 3:11 I indeed baptize you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and [with] fire:
Whilst the baptism of the Holy Ghost was 1st announced by John the Baptist it never seen its fulfilment until the day of Pentecost.
Acts 1:4-5 confirms its fulfilment: And, being assembled together with them, commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which, saith he, ye have heard of me. For John truly baptized with water; but ye shall be baptized with the Holy Ghost not many days hence.”
Christ applied the realization of this promise of the baptism of the Holy Spirit to the day of Pentecost that was approaching. This was indeed “the promise of the Father.”
Even though these disciples were Christians Christ was telling them that they needed a power from the Holy Ghost that would propel them to decimate the kingdom of darkness.
Christ also said in Luke 24:46-49: “Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. And ye are witnesses of these things. And, behold, I send the promise of my Father upon you: but tarry ye in the city of Jerusalem, until ye be endued with power from on high.”
The promise of the Father was the baptism of the Holy Ghost which was a power from on high that endued them for service.
Peter said about this same baptism, in Acts 2:38-39, “Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.”
The Lord continues in Acts 1:8 on the same subject: “But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.”
Where all the disciples converted on (and before) the actual day of the day of Pentecost? Of course! Scripture proves that the disciples were all saved at the time of John or thereafter, and all were soundly saved by the time they reached the day of Pentecost.
Jesus said in Mark 9:1 to the disciples: “Verily I say unto you, That there be some of them that stand here, which shall not taste of death, till they have seen the kingdom of God come with power (or dunamis).”
Whilst Christ introduced the kingdom with His earthly ministry, the kingdom of God did not “come with power” until Pentecost. The Holy Ghost falling upon them equipped the disciples to take the Gospel out into the nations, with remarkable courage, strength and success.
The Greek word here for “power” is dunamis – where we get the English words dynamite or dynamo from.
God was saying that the kingdom of God was soon going to be explosive. Believers were going to have a turbo put into their engine that would embolden them to invade the nations with the glorious Gospel of Christ.