Acts 1:8 comes from the mouth of Jesus before He ascends to Heaven. He states: “but you will receive power when the Holy Spirit has come upon you; and you shall be My witnesses both in Jerusalem, and in all Judea and Samaria, and even to the remotest part of the earth.”
This statement from Jesus is a sequel to the commission He gave to the disciples and also a continuation of Luke’s account from Luke 24:44-49. Here the passage reads: “He said to them, ‘This is what I told you while I was still with you: Everything must be fulfilled that is written about me in the Law of Moses, the Prophets and the Psalms.’ Then he opened their minds so they could understand the Scriptures. He told them, ‘This is what is written: The Messiah will suffer and rise from the dead on the third day, and repentance for the forgiveness of sins will be preached in his name to all nations, beginning at Jerusalem. You are witnesses of these things. I am going to send you what my Father has promised; but stay in the city until you have been clothed with power from on high.’”
Here is the question. Is Acts 1:8 itself a reiteration of this passage in Luke? I believe it is. Only this time, Luke provides greater detail. Darrell Bock even contends that Acts 1:8 overlaps the account in Luke. Both accounts provide the reasoning that the disciples remained in Jerusalem even amidst the turmoil towards believers in Christ.
This particular passage lays some very solid groundwork for the story Luke will convey in Acts. Jesus had already brought the Gospel to the Jews, the Romans, and the Samaritans with varying results. It should have become clear sooner that His ministry was for all nations and the earth entirely. The focus has officially shifted from a regional ministry to a broader, more global ministry.
Gary Burge and Andrew Hill write: “the phrase ‘to the ends of the earth’ appears only four times in the Old Testament, in Isaiah (8:9; 48:20; 49:6; 62:11), where it points to the Gentiles. Therefore, this phrase most likely refers to this ethnic group rather than a precise geographical locale such as Spain or Rome.”
This must have been overwhelming for the disciples. They were now expected to step out of the small region they were familiar with and venture into new frontiers. Think about it for a minute. What knowledge did they have of the languages, customs, and cultures in these other nations? I would imagine they lacked sufficient knowledge to lead a global mission.
This is where the Holy Spirit comes in. We know that the Holy Spirit does arrive at Pentecost in Acts 2. One of the effects on the disciples was the knowledge of the various languages of different nations. I contend that another effect was the knowledge they gained about the different cultures and the courage to reach out to them.
Luke 24:45 states: “Then he opened their minds so they could understand the Scriptures.” With that understanding came a portion of God’s intent for the Gospel message spreading. The disciples would need to be equipped and capable to answer the call. The Holy Spirit certainly enabled that.
The Holy Spirit bringing courage to reach out to varying cultures is apparent in a big way right off the bat: Peter’s sermon in Acts 2:14-41. Yes, the same Peter that denied Christ was now boasting about Him. The same Peter that could only keep his eyes on Christ for a second during a storm is now standing firm in the face of a chaotic society and time. Only the Holy Spirit can provide such strength.
The significance of Acts 1:8 is clear. The Holy Spirit has provided a means for realizing God’s plan. That plan is redemption. Not just for the Jews, but for all of mankind.
Bock, Darrell L. Acts, From the Baker Exegetical Commentary on the New Testament. 1st ed. Grand Rapids, MI: Baker Academics, 2007. p. 52.
 Not yet referred to as “Christians”. That term originates in Antioch in Acts 11:26.
Burge, Gary M. and Hill, Andrew E. The Baker Illustrated Bible Commentary. Grand Rapids, MI: Baker Publishing Group, 2012. p. 1170.