The very first verse tells how to deal with one weak “in the faith”, the same expression in Greek and English (Acts 6:7; 13:6; 14:12; 16:5), where it is clear that “the faith” refers to the system of faith, which is the New Testament gospel system. While this chapter does deal with matters that pertain to “the faith” (v. 1) – it deals with those matters of “the faith” that govern a Christian’s personal conduct before God. The chapter is not dealing with moral matters (questions of what is morally right or wrong). Included in this moral law are things that Paul would refer to as being right (“clean”) or wrong “unclean of (themselves)” (v. 14). These are things that man is without excuse for forgetting or not knowing (Rom. 1:18 -32). This chapter does not deal with lying, stealing, adultery, licentiousness, fornication, homosexuality, drunkenness and similar sin, as these are not matters based on ones personal faith because they have already be condemned by the law of Christ. Those weak in the faith are equated to those weak in knowledge in 1 Corinthians 8. Their knowledge and discernment under the faith had not yet developed to the point of the strong in non-doctrinal matters such as eating meat offered to idols. The strong are required to bear with them in their weakness of thinking this was a sin, while they realize that an “idol” is nothing and therefore the meat is acceptable. The weak should not be allowed to judge (condemn) the strong because they eat this meat. Each should allow the other to practice these non-doctrinal matters as he believes“the faith” requires of him in an atmosphere of peace, patience and learning – an atmosphere conductive to growing in the faith. As long as each keeps “it to himself before God” (v. 22), that is to say he does not make it a condition of “receiving” (v. 1) the other, they can still work together in those things that they must do in common (congregational matters).
This chapter is not dealing with the fundamentals of the faith, or the “first principles of the doctrine of Christ.” The Romans receiving this letter were already “in the faith”, though some were weak in it. To be in the faith they would have had to believe and obey the first principles of the gospel. So, it is not talking about working together while holding to different doctrines involving those fundamental matters. This chapter is not dealing with questions of congregational practice. There is not one thing in the chapter that deals with what Christians are do together as a church before God. Everything in the chapter deals with personal conduct regarding personal morality. Examples today would be things like having a Christmas tree in the house or celebrating Halloweeen. For some their conscience allows it while other do not participate. In such matters of personal (and morally right) conduct there can be “unity in diversity”, which is a far cry from the “unity in diversity” advocated by some regarding doctrinal matters. However, when it comes to matters of corrupting congregational worship and work there can be no “unity in diversity.” When the instrument was introduced into congregational worship division came because it forced those who opposed it to sing with it or not sing at all. In either case it would violate their consciences, so they had to worship separately and mark those who brought it in as “those who cause divisions.” (Rom. 16:17).
Again, I emphasize, Romans 14 does not cover matters of “the faith” that apply to congregational activity, but those matters (right within themselves) that apply to individual personal practices where Christians may differ while they grow together (Eph 4:13 [KJV]) Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ: