Cambridge Greek Testament Commentary
Romans 15 - Introduction
15. (1) The fundamental Christian principle is mutual service and help, after the model of the Christ, and in that endurance and encouragement which GOD gives to promote harmony in His service.
(7) This mutual service and reception is the proper consequence in the Christian life, of Christ’s service and reception of Jew and Gentile unto GOD’s glory, the foundation of the hope, joy and peace of all Christian men.