Acts 12:24-13:3 :
But the word of God grew and multiplied. Barnabas and Saul returned to Jerusalem, when they had fulfilled their service, also taking with them John whose surname was Mark.
Now in the assembly that was at Antioch there were some prophets and teachers: Barnabas, Simeon who was called Niger, Lucius of Cyrene, Manaen the foster brother of Herod the tetrarch, and Saul. As they served the Lord and fasted, the Holy Spirit said, “Separate Barnabas and Saul for me, for the work to which I have called them.”
Then, when they had fasted and prayed and laid their hands on them, they sent them away.
Here we get a good look at what it is like to be a servant of Jesus. When Barnabas and Saul were done with “their service,” they went back home to Jerusalem. Barnabas and Saul’s service didn’t really end though because we later find them back in Antioch with a group of teachers and prophets. It says that they “served the Lord and fasted.” It doesn’t really tell us how they were serving the Lord. We do know that prayer is a very real service to the Lord and whatever they were doing, it was the right thing to do because the Holy Spirit was there to give them their next set of instructions. They were to send Barnabas and Saul back out. It also doesn’t tell us how the Holy Spirit told them, but they knew that it was Him somehow.
Servants of God serve by going places and by staying in places. They can serve by teaching, prophesying, and praying. Whatever they do, they always take their instructions from the Lord because that’s what a servant does.