Harmony through Self-renouncement.
Romans 15:1 f. Strength carries with it the duty of bearing others-' weaknesses, not of pleasing oneself (cf. 1 Corinthians 10:33). The strong are men of robust faith, in contrast with the weak of Romans 14:1. The Christian is to please his neighbour not by humouring his failings, but by aiming at his good, with a view to building him up in faith and character (cf. Romans 14:19).
Romans 15:3. So the Christ bore Himself, according to Psalms 69 (quoted above in Romans 11:9; cf. Matthew 27:27 ff., etc.). The Psalmist in suffering reproach for God imaged our Lord's self-negation.
Romans 15:4 reflects, in view of the above reference, on the value of Scripture, which trains us to patience and hope. Like the story of Abraham's faith (Romans 4:23), that of the Psalmist's grief was written for our instruction.
Romans 15:5 f. May the God who thus gives endurance and encouragement, grant to you a harmonious mind (an echo of Romans 12:16) according with that of Christ Jesus (cf. Romans 15:3, Php_2:2-5). Your harmony will yield a concert of praise to God, uttered as if with one mouth.