The reading is from Acts of the Apostles 15:35-41

IN THOSE DAYS, Paul and Barnabas remained in Antioch, teaching and preaching the word of the Lord, with many others also. And after some days Paul said to Barnabas, "Come, let us return and visit the brethren in every city where we proclaimed the word of the Lord, and see how they are." And Barnabas wanted to take with them John called Mark. But Paul thought best not to take with them one who had withdrawn from them in Pamphylia, and had not gone with them to the work. And there arose a sharp contention, so that they separated from each other; Barnabas took Mark with him and sailed away to Cyprus, but Paul chose Silas and departed, being commended by the brethren to the grace of the Lord. And he went through Syria and Cilicia, strengthening the churches.