What does Acts 13:3 mean?

The leadership of the church in Syrian Antioch, including Barnabas, Simeon, Lucius, Manaen, and Saul, have been praying and fasting. The Holy Spirit responds to them, telling them to commission Barnabas and Saul for special work: to travel and spread the story of Jesus and His offer of salvation and forgiveness (Acts 13:1–2).

Where before the group was fasting and praying either in search of guidance or as part of their normal worship, now they do so to seek blessing for Barnabas and Saul. They lay their hands on the two to show they authorize their commissioning. They are not endowing Barnabas and Saul with special spiritual gifts, as Barnabas is already a prophet and Saul is a teacher. And they're certainly not giving them the Holy Spirit—Barnabas received the Holy Spirit in Jerusalem (Acts 4:36–37; 11:22–24), and Saul when Ananias laid his hands on him (Acts 9:17).

Barnabas had first come to Syrian Antioch when the church leaders in Jerusalem heard that Gentiles there had accepted Christ. To effectively reach more people, Barnabas sent for Saul in nearby Tarsus (Acts 11:19–26). Now that church has grown enough to send the two on. After Barnabas and Saul finish their missionary journey, they will return to Antioch and report the Holy Spirit's work (Acts 14:26–27). One of the purposes of the church is to spread the news about Jesus and establish new churches. Syrian Antioch is a good example of this.