To reign in life is to be under the ruling of the divine life. If we look at the life of the Lord Jesus as the God-man in His humanity on the earth, He was absolutely under the ruling of the divine life of the Father. Everything He did was under the Father's ruling. As a man, He rejected His natural humanity and lived a human life under the restriction of the divine life of His heavenly Father. By practically being under the ruling of the divine life of the Father, He was reigning in life. This is the pattern we should follow.
By living under the rule of the divine life, by reigning in life, we can live the church life. There is no possibility for us to live the church life if we are not under the ruling and control of the divine life. We must reign in life to live the church life.
Romans 14:1—15:13 covers our reigning in life in the church life. The reason why there are so many divisions among Christians today is that their receiving of the believers is not under the restriction, the control, of the divine life. If all Christians would receive one another according to the divine life, all divisions would be gone. Only by reigning in life can we receive all whom God has received.
We must receive the believers according to God's receiving (14:1-23). God is our example as to how we should receive one another. In writing this chapter, Paul's heart was tolerant, his attitude was broad, and his view was noble. In order to practice the church life that he introduced in chapter twelve, we must strictly observe the matters set forth in chapter fourteen. Many saints who love the Lord and seek to live the church life have failed because they were either negligent or mistaken in this matter. In order to practice the church life revealed in chapter twelve, we must learn the practical lessons of receiving the believers, that the church life may be all-inclusive, able to include all kinds of genuine Christians. For this, we must all be under the reigning of the divine life.
Our receiving of the believers under the reigning in life is first according to God's receiving and then according to Christ's receiving (15:1-13). We should receive one another in the same way that Christ receives us. The strong ones need to bear the weaknesses of the weak, not pleasing themselves but pleasing the brothers and sisters for their building up, even as Christ did not please Himself but bore God's reproach (vv. 1-4). We should be of the same mind toward one another according to Christ Jesus so that with one accord we may glorify God in receiving one another as Christ also received us to the glory of God (vv. 5-7). Christ has become a minister of both the circumcision and the Gentiles that the God of hope may fill us with all joy and peace for us to abound in hope in the power of the Holy Spirit (vv. 8-13).