Paul now turned to the second major quality that he introduced in 1:27-30, namely steadfastness in the face of opposition to the gospel (cf. 1:7, 28). He had introduced the idea of joy in the face of opposition earlier (1:19, 28-30; 2:17-18). He would discuss how to face overt persecution later (4:4-9).
There were two main sources of opposition that the Philippians faced as they sought to have fellowship with Paul in the proclamation of the gospel. Paul dealt with both of these. However, he began with a charge to rejoice in the Lord and ended this section with a summary exhortation.