Acts 1:2

Jesus was "taken up" at His ascension (Luke 24:51). The orders that He had given His apostles were that they should remain temporarily in Jerusalem (Acts 1:4; Luke 24:49). Then they should go out into the whole world to herald the good news of salvation (Acts 1:8; Luke 24:47; Matthew 28:19-20).

Apostles are by definition sent ones. However this term here has specific reference to the few disciples to whom Jesus gave this command personally. Their calling was unique; these men laid the foundation of the church (Ephesians 2:20). All Christians are apostles in the sense that Christ has sent all of us on this mission. Yet the 12 apostles (and Paul) were a unique group with special powers the Lord did not give to the rest. [Note: See Robert D. Culver, "Apostles and the Apostolate in the New Testament," Bibliotheca Sacra 134:534 (April-June 1977):131-43.]

"Each of these four factors-the witness mandate, the apostles, the Holy Spirit, the ascended Lord-is a major emphasis that runs throughout Acts; each receives special attention in chapters 1 and 2." [Note: Longenecker, p. 253.]