We usually assume that when Jesus said, after the resurrection, “But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.”, that Jesus was speaking only or primarily to the apostles. However, when the persecution broke out in Jerusalem, it was everyone “except the apostles”, who were scattered into Judea and Samaria and preached the Word wherever they went.
The apostles remained in Jerusalem at first, as the primary witnesses in the spiritual core of the world, where Jesus’ death and resurrection occurred and the Spirit came down upon the Church, and to serve as an anchor of faith for the rest of the Church, standing firm in His resurrection in the face of death, because Jesus had given them many convincing proofs that He was alive. The rest of the Church became the first witnesses everywhere else. This should affirm all those who know that they are called to be His witnesses in the power of the resurrection, as well as the apostles, even to the ends of the earth.