John Calvin Commentary Romans 14:5

"One man esteemeth one day above another: another esteemeth every day [alike]. Let each man be fully assured in his own mind." — Romans 14:5 (ASV)

One indeed, etc. He had spoken before of scruples in the choice of meats; he now adds another example of difference, that is, concerning days, and both these arose from Judaism. For as the Lord in his law made a distinction between meats and pronounced some to be unclean, prohibiting their use, and as he had also appointed festal and solemn days and commanded their observance, the Jews, who had been brought up from their childhood in the teaching of the law, would not lay aside that reverence for days which they had held from the beginning and to which they had been accustomed throughout their lives. Nor could they have dared to touch those meats from which they had so long abstained.

That they were imbued with these ideas was an evidence of their weakness; they would have thought otherwise had they possessed a certain and clear knowledge of Christian liberty. But in abstaining from what they thought to be unlawful, they showed piety, as it would have been a proof of presumption and contempt had they done anything contrary to the promptings of their conscience.

Here then the Apostle applies the best rule, when he instructs everyone to be fully assured in his own mind. By this, he intimates that there ought to be in Christians such a concern for obedience that they do nothing except what they think, or rather feel assured, is pleasing to God.

And this ought to be thoroughly kept in mind: it is the first principle of right conduct that individuals should be dependent on the will of God and never allow themselves to move even a finger while their minds are doubtful and wavering. For it cannot be otherwise than that rashness will soon turn into obstinacy when we dare to proceed further than what we are persuaded is lawful for us.

If anyone objects, saying that infirmity is always perplexing and that, therefore, such certainty as Paul requires cannot exist in the weak, the plain answer to this is that such individuals are to be pardoned if they keep themselves within their own limits.

For Paul’s purpose was no other than to restrain excessive liberty, which leads many to thrust themselves, as it were, randomly into matters that are doubtful and unresolved. Therefore, Paul requires that this be adopted: that the will of God is to preside over all our actions.