John Calvin on Romans 14:4

4. Who art thou who judgest, etc. “As you would act uncourteously, yea, and presumptuously among men, were you to bring another man’s servant, under your own rules, and try all his acts by the rule of your own will; so you assume too much, if you condemn anything in God’s servant, because it does not please you; for it belongs not to you to prescribe to him what to do and what not to do, nor is it necessary for him to live according to your law.”

Now, though the power of judging as to the person, and also as to the deed, is taken from us, there is yet much difference between the two; for we ought to leave the man, whatever he may be, to the judgment of God; but as to his deeds we may indeed form a decisive opinion, though not according to our own views, but according to the word of God; and the judgment, derived from his word, is neither human, nor another man’s judgment. Paul then intended here to restrain us from presumption in judging; into which they fall, who dare to pronounce anything respecting the actions of men without the warrant of God’s word.

To his own Lord he stands or falls, etc. As though he said, — “It belongs rightly to the Lord, either to disapprove, or to accept what his servant doeth: hence he robs the Lord, who attempts to take to himself this authority.” And he adds, he shall indeed stand: and by so saying, he not only bids us to abstain from condemning, but also exhorts us to mercy and kindness, so as ever to hope well of him, in whom we perceive anything of God; inasmuch as the Lord has given us a hope, that he will fully confirm, and lead to perfection, those in whom he has begun the work of grace.

But by referring to the power of God, he means not simply, as though he had said, that God can do this if he will; but, after the usual manner of Scripture, he connects God’s will with his power: and yet he speaks not here of perpetuity, as though they must stand to the end whom God has once raised up; but he only reminds us, that we are to entertain a good hope, and that our judgments should lean this way; as he also teaches us in another place,

“He who began in you a good work, will perform it to the end.” (Philippians 1:6.)

In short, Paul shows to what side their judgments incline, in whom love abounds.

Romans 14:5-6

5. One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.

5. Hic quidem diem prae die aestimat; ille autem peraque aestimat omnem diem. Unusquisque sententiae suae certus sit.

6. He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it. He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.

6. Qui curat diem, Domino curat; qui non curat diem, Domino non curat. Qui vescitur, Domino vescitur, gratias enim agit Deo; et qui abstinet, Domino abstinet, et gratias agit Deo.