Power From On High
Luke 24:44 And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me.
Luke 24:45 Then opened he their understanding, that they might understand the scriptures,
Luke 24:46 And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day:
Jesus explains to them the gospel of salvation
Luke 24:47 And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem.
Repentance, a change of mind, and coming to Jesus for the remission of sins. This should be preached in the name of God, in Jesus' name beginning where you are and among all nations.
Luke 24:48 And ye are witnesses of these things.
You have seen these things and are to be witnesses, but you will need God's power, the Holy Spirit.
Luke 24:49 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.
This power of the Holy Ghost came down at Pentecost.
Acts 2:1 And when the day of Pentecost was fully come, they were all with one accord in one place.
Acts 2:2 And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.
Acts 2:3 And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
Acts 2:4 And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
This was not for show, nor an end to itself, but the presence of God the Holy Spirit, the teacher to be with you, giving you power to witness the gospel message and to serve him.