The ‘therefore’ of verse 1 shows the arbitrary nature of the current chapter divisions. Here we see the corporate nature of our faith. Why go on living? At least in part, it is to comfort others with the “comfort of love” we receive, as a result of the “consolation in Christ.” Not just the consolation of Christ, but the consolation in Christ, that which comes as a result of our union with him (v. 1a). The salvation from God (1:28), which resulted in our belief and participation in the suffering of Christ specifically, is as a result of the conflict from those who are opposed to him (1:29-30). In other words, it is not any suffering which all people may experience, but that which is unique to being a follower of Christ.
Another word for consolation here may be ‘encouragement’. Paul knew something of the discouragement that can come with trying to minister Christ and his word to a hostile world. Note how important it was to have Barnabas, meaning an encourager, with him at times – Acts 11:19ff. Fellowship in the Spirit, is also a crucial help for each of us in our walk and service, especially “any affection and mercy.” (v. 1bc) Moreover, learning of this cooperative fellowship brought a fullness of joy to Paul – a unity in their diversity, so to speak – “being like-minded, having the same love, being of one accord, of one mind.” (v. 2) In short, they shared the same attitude toward each other.
The opposing attitude is one of “selfish ambition and conceit.” (v. 3a) There was rather a unity possible through humility. In “lowliness of mind let each esteem others better than himself.” (v. 3bc) There is an individual responsibility toward the others members of the body to look out not only for one’s own interests, “but also for the interests of others.” (v. 4) Note that it is not wrong to look after one’s own interests (Mt. 22:39; Mk. 12:31), since no one ever really hates their own body (Eph. 5:29). Paul made this same point in his letter to the Romans, based upon the example of the Christ (15:1-3). One who loves, does not seek their own interests at the expense of others (I Cor. 13:5).