John Calvin Commentary Romans 13:9

"For this, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not covet, and if there be any other commandment, it is summed up in this word, namely, Thou shalt love thy neighbor as thyself." — Romans 13:9 (ASV)

For this, You shall not commit adultery, etc.. From this passage, it cannot be concluded what precepts are contained in the second table, for he adds at the end, and if there is any other precept. He indeed omits the command concerning the honoring of parents; and it may seem strange that what especially belonged to his subject should have been overlooked.

But what if he had left it out to avoid obscuring his argument? Though I dare not affirm this, I see here nothing lacking to answer his intended purpose, which was to show: that since God intended nothing else by all His commandments than to teach us the duty of love, we should by all means strive to fulfill it.

And yet the uncontentious reader will readily acknowledge that Paul intended to prove, by similar examples, that the meaning of the whole law is that we should practice love for one another, and that what he left implied should also be understood, namely—that obedience to magistrates is not the least important thing that tends to foster peace and preserve brotherly love.