Some have explained the contention [between Paul and Barnabas] by noting a possible spiritual decline in the change from the words: “the Holy Spirit said,” in13:2, to the words: “Paul said,” in 15:36. It should be remembered, however, that in the former passage we have the Spirit’s original instruction to the church at Antioch to separate Paul and Barnabas for the work wherein they had now become engaged. Therefore we should not expect another such case, nor are we to suppose that the apostle is acting in the flesh every time we fail to find the words: “The Holy Spirit said.” Indeed, since the passing of the Pentecostal era believers should be very careful about saying: “The Spirit said” or, “The Spirit told me” or, “The Lord said to me,” unless they are referring to the written word of God. — Stam, page 13.
It was Paul’s love for the people in the churches he started that prompted him to begin his second journey. The Spirit, as we will see, had more in mind for him than simply revisiting places he’d already been.
Paul and Barnabas’ contention may have resulted, in part, from Barnabas’ leaning toward the Judaizers (Galatians 2:13).