John Calvin on Acts 13:3

3. When they had fasted and prayed. That they may obey the oracle, they do not only send Paul and Barnabas away; but also with a solemn rite they appoint them to be the apostles of the Gentiles; it is without question that this was a public fast. Luke said before, that they were fasting, forasmuch as they were busied in their ministry: it might be that that was according to the custom; but now there is another reason, for in appointing a public fast, which used to be done in hard matters and of great importance, they provoke both themselves and others unto an earnest ferventness in prayer, for this is oftentimes added in Scripture as a help to prayer; but (it was a matter of such weight to erect the kingdom of Christ amongst the Gentiles) the teachers of Antioch do not without cause earnestly pray the Lord, that he will enable his servants; “Ut det pares servis suis humeros,” that he may make the shoulders of his servants equal to the burden, may fit them for the office. and that was not the end of their prayer, that God would, by his Spirit of wisdom and discretion, govern their judgments in choosing, because all disputation or doubting concerning this matter was taken away; but that God would furnish those with the Spirit of wisdom and strength whom he had already chosen to himself, that he would strengthen them with his power against all the invasions of Satan and the world, that he would bless their labors, that they might not be unfruitful, that he would open a gate for the new preaching of the gospel.

The laying on of hands which Luke reckoneth up, in the third place, was a kind of consecration, as we have said, (Acts 6:6.) For the apostles retained the ceremony which was used amongst the Jews, according to the old custom of the law; as also kneeling, and such rites, which were profitable to exercise godliness. In sum, this is the end why they laid their hands upon Barnabas and Paul, that the Church might offer them to God, and that they might with their consent declare that this office was enjoined them by God; for the calling was properly God’s alone, but the external ordaining did belong to the Church, and that according to the heavenly oracle.

Acts 13:4-12

4. Therefore, when they were sent forth by the Holy Ghost, they went to Seleucia, and thence they sailed into Cyprus. 5. And when they were at Salamis, they preached the word of God in the synagogues of the Jews; and they had John, also for their minister. 6. And when they had passed over the island unto Paphos, they found a certain false prophet, a Jew, named Bar-jesus, 7. Who was with Sergius Paulus, the proconsul, a wise wan; who, when he had called Barnabas and Paul, sought to hear the word of God. 8. And Elymas, the sorcerer, (for so is his name expounded,) resisted them, seeking to turn away the proconsul from the faith. 9. And Saul, which was also called Paul, being full of the [Holy] Ghost, and looking steadfastly on him, 10. Said, O thou that art full of all deceit and wickedness, thou son of the devil, thou enemy of all righteousness, dost thou not cease to pervert the straight ways of the Lord? 11. And now, behold, the hand of the Lord is upon thee, and thou shalt be blind, not seeing the sun for a time. And forthwith there fell upon him mist and darkness, and, going about, he sought some to lead him by the hand. 12. Then the proconsul, seeing what had happened, he believed, wondering at the doctrine of the Lord,