John Calvin Commentary Acts 15:3

"They therefore, being brought on their way by the church, passed through both Phoenicia and Samaria, declaring the conversion of the Gentiles: and they caused great joy unto all the brethren." — Acts 15:3 (ASV)

Being brought on the way by the Church. Since, by the common consent of the Church, companions were joined to Paul and Barnabas to escort them as a matter of duty, we may gather from this that all the godly were on their side and that they never thought otherwise than that the cause was theirs as much as it was the apostles'.

Therefore, they resolved upon the journey of Paul and Barnabas with the same mindset with which they undertook it: namely, that they might subdue and silence those troublesome individuals who falsely claimed the apostles' endorsement. Furthermore, when he states shortly thereafter that on their journey they informed the brothers and sisters of the wonderful conversion of the Gentiles, this serves as a testimony and a sign that they did not come to Jerusalem filled with fear; rather, they fearlessly and boldly professed what they had previously taught.

Therefore, they did not come to plead their case before judges, but so that, with mutual consent and judgment from both sides, they might approve what God had commanded concerning the abolition of ceremonies. For although they did not undervalue the judgment of the apostles, yet because they knew it was not lawful either for them or for the apostles to decree otherwise concerning this matter, it was not fitting for them to stand like defendants whose case is being tried in court.

From this came their bold rejoicing; the joy of the godly serves this purpose, through which they affirm both Paul's doctrine and the calling of the Gentiles.