Paul says, “Therefore accept one another;” and tells us the rationale for doing this, adding: “just as the Messiah accepts you, to the glory of God.”
God gives you both “endurance and encouragement” so that He “allows you to live in harmony with one another.” (Romans 15: 4) He gives you these gifts in order that you are able to “glorify the God and Father of our Lord Jesus Christ.” (Romans 15: 6) And what imputes glory to God? Lo and behold, what brings glory to God is “a united mind and voice.”
Notice it is God who “allows” us to live in harmony; He provides “endurance and encouragement” so that we are able to be “united” in both “mind and voice.” Much of this endurance and encouragement are given to us through “whatever was written in the past…for our instruction.” Of course, the main source of this endurance and encouragement is directly from God, the Holy Spirit who is dwelling within us, working His will through us.
Paul’s “therefore” relates back to his argument that unity among Christians brings glory to God the Father. This is Paul’s rationale for having “a united mind and voice.” As we show the world our unity, God is glorified. Unfortunately, Christians are fragmented into so many denominations with some so adamant that their way is the only way, unbelievers are wary and sometimes downright terrified of all Christians.
Therefore, Paul begs us to live in harmony with one another so that we may glorify God, especially among unbelievers.