Paul is encouraging his readers to accept one another. He mentions that in the Old Testament, God had given commands to the Israelites about the observance of certain days, mainly connected to the annual feasts such as the Passover and Pentecost. We can understand how Jews, after they were converted, would want to practice those occasions (indeed Paul later would be arrested because he participated in a religious event at the temple in Jerusalem). Such would find it hard to understand why Gentiles, when they were converted, did not have any wish to keep those occasions. Yet Paul, under the guidance of the same Spirit who guided the composition of Leviticus, makes it clear that the Gentiles did not have to keep them.
Paul here is not suggesting that the weekly Sabbath has come to an end and that Christians don’t need to observe it. The fact that it is called the Lord’s Day, and that it was the day when Christians met to worship God, indicates that it is still a holy day binding on everyone, but especially on God’s people. Yet there can be other types of days that some people may want us to observe as Christians.
What do we do when someone does not practice what we regard as beneficial? Paul tells us that we have to ask, ‘What does the Master say?’ and, ‘Is the Master helping that believer to stand even if he does not do what we do?’ What we cannot say is that the individual is disobeying Jesus. Instead we have to decide for ourselves if the practice of certain activities is helpful for ourselves and leave it there.
How will we know that we have reached a right conclusion? We will know if we are honouring the Lord and living thankful lives.