I would like to quote that verse along with two other passages and then we will seek to answer your good question.

“Behold, I send the Promise of the My Father upon you; but tarry in the city of Jerusalem until you are ENDUED WITH POWER FROM ON HIGH” (Luke 24:49…NKJV).

“But YOU SHALL RECEIVE POWER when the Holy Spirit has come upon you; and YOU SHALL BE WITNESSES TO ME IN JERUSALEM, and in all Judea and Samaria, and to the end of the earth” (Acts 1:8).

“When the Day of Pentecost had fully come, they were all with one accord in one place. And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. Then there appeared to them divided tongues, as of fire, and one sat upon each of them. And THEY WERE ALL FILLED WITH THE HOLY SPIRIT and began to speak with tongues, AS THE SPIRIT GAVE THEM UTTERANCE” (Acts 1:1-4).

In the first two references (Luke 24:49 and Acts 1:8) Jesus was speaking to His disciples just before He ascended back to heaven. He knew that a big change would take place in their lives in His absence for they were about to become HIS WITNESSES to the world. They would be privileged to preach the good news of His sacrificial death on the cross and His glorious resurrection and all who would believe on the Lord Jesus Christ as their Savior would be saved. Jesus had already told them of this commission, “Go into all the world and preach the gospel to every creature. He who believes and is baptized will be saved; but he who does not believe will be condemned” (Mark 16:15-16). In Luke 24:49 He told them what would enable them to carry out this commission; He would “send the Promise of My Father” and they would be “endued with power from on high.” The “Promise of My Father” was the Holy Spirit (John 14:15-17).  The Holy Spirit would “come upon them” and empower them to preach the gospel. Jesus brought this out clearly in His Upper Room ministry: “But when the Helper comes, whom I shall send to you from the Father, the Spirit of truth who proceeds from the Father, He WILL TESTIFY OF ME. AND YOU ALSO WILL BEAR WITNESS, because you have been with Me from the beginning” (John 15:26-27). This was confirmed also in Acts 1:8 but we learn the main reason why the coming of the Spirit would take place at Jerusalem, for their gospel testimony would “begin at Jerusalem” (and eventually spread out into all the world). Jerusalem is where Jesus was rejected and crucified and yet the message of salvation would be preached first to those who were the guiltiest. Amazing grace!

In Acts 2:1-4 we have the actual account of the Spirit coming upon the disciples and filling them so they would have the power to boldly present Christ to their fellow-Jews in Jerusalem. The Apostle Peter preached Christ to them and three thousand souls were saved that very day (see verses 22-41). Think of it, the disciples of Christ were cowering in fear after Christ’s death (see John 20:19 and Luke 24:36-37), but after the Spirit was given to them, they became BOLD WITNESSES for Christ (Acts 4:31). In closing, may I remind my fellow-believers that we too have received the Holy Spirit (Ephesians 1:13) and thus we too have the power to enable us to be WITNESSES FOR CHRIST. Are you boldly proclaiming the gospel of Christ to your unsaved loved ones, friends, neighbors, co-workers, and to those you may meet outside of your community?  (DO)  (644.3)