John Calvin Commentary 1 Corinthians 7:10

"But unto the married I give charge, [yea] not I, but the Lord, That the wife depart not from her husband" — 1 Corinthians 7:10 (ASV)

To the married I command. He now addresses another condition of marriage—its being an indissoluble tie. Accordingly, he condemns all those divorces that were a daily occurrence among the Gentiles and were not punished among the Jews by the law of Moses. Let not, he says, the husband put away his wife, and let not the wife depart from her husband. Why? Because they are joined together by an indissoluble bond.

It is surprising, however, that he does not make an exception, at least in case of adultery, for it is not likely that he intended to curtail in any way the doctrine of Christ. To me, it appears clear that the reason he has made no mention of this is that, as he is discussing these things only in passing, he chose rather to refer the Corinthians to the Lord’s permission or prohibition than to go over everything in detail. For when people intend to teach anything concisely, they content themselves with a general statement. Exceptions are reserved for a more detailed and extensive discussion.

But as to what he adds—not I, but the Lord—he indicates by this clarification that what he teaches here is taken from the law of God. For other things that he taught he also had from the revelation of the Spirit, but he declares that God is the author of this, in that it is expressly taken from the law of God. If you ask about the particular passage, you will nowhere find it in so many words; but as Moses testifies in the beginning that the connection between a husband and wife is so sacred that for its sake a man ought to leave his father and mother (Genesis 2:24).

From this, it is easy to gather how inviolable this connection is. For by natural right, a son is bound to his father and mother and cannot shake off that yoke. Since the connection of marriage is preferred to that bond, much less ought it to be dissolved.