Romans 14
"For the kingdom of God is not eating or drinking, but righteousness, peace, and joy in the Holy Spirit" (v17). The gospel grew up in a multi-cultural world. Born among observant Jews, it quickly throughout the Roman Empire. Believers had to distinguish between moral codes and cultural codes. What can we eat or drink, which day shall we worship? Paul taught that love should motivate our decisions, not the desire to be "right" (v15).
When we disagree, we are commanded to "pursue the things that make for peace and the building up of one another" (v19).