Romans 14:5
One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind. One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.
Romans 14:5 means that people may legitimately differ in how they regard days, and in other matters of conscience that are not grounds for division. In such matters each person is to be fully convinced and fully persuaded in his own mind. That persuasion is personal, calling for freedom to think and to follow personal conviction according to reason, self-control, principle, and sound judgment, rather than expecting another person to prescribe an exact rule.
No one may control another's mind, judge for another, prescribe another's duty, or require the surrender of personal individuality. No one is to be forced to adopt another person's practice, for Christ's kingdom does not rule by oppression or compulsion. Differences of opinion in these conscientious matters are not to disrupt unity among brethren.
Applied to Sabbath observance, the conscience of one who keeps the Sabbath is to be treated with the same tenderness and respect as the conscience of one who does not keep it. Applied to diet, conscientious believers may differ, for example over eating butter, and what is suitable cannot be fixed by one person for everyone. Believers are not to become preoccupied with food and drink, but to exercise sound judgment for themselves.