A phrase often used by brethren is, “In matters of faith, unity; in matters of opinion, liberty; in all things, charity.” The phrase is a good one, for a basic practice among Christians is not to insist on issues that do not affect salvation.
The faith you have, keep to yourself before God. Blessed is the one who does not judge himself by what he approves.
Romans 14:22 NET
It is possible to destroy a brother, because of his lack of faith on a question of opinion, by approving and insisting upon a practice. Whoever does this brings condemnation upon himself.
In matters of opinion, salvation is not affected. In the context, Paul speaks of the type of food one eats at home or the individual observance of special days. Among us today, for example, some Christian families do not observe holidays such as Christmas. These things should remain between the person and God. That means they should not be subjects that divide the church or questions of faith among brethren, for such opinions do not change anyone’s eternal destiny.
The faith that brings salvation, however, must always be something that does not remain between the Christian and God, but a subject to be raised with everyone all the time.