It is the mark of proven and highest piety that you should reckon my counsel too worth consulting concerning causes pertaining to your pontificate. That you do this you show, not, as you said, out of a mind of uncertainty, but of love. Wherefore, against the fault which you indicated in your letter, I judge that you are rightly moved. For who, even a layman, would not perceive that a marriage arising from the nearness of affinity comes about not without great stain? Hence, although a most just grief over the necessity of that very strictness weighs upon your solicitude, yet he is wholesomely chastened in temporal things whom we desire to be saved in things eternal.
It behooves, therefore, that the man — the husband, namely, of two sisters — be struck, not with an irrevocable anathema, but, with observances laid down, be for the time being sequestered from the Church. And since you indicate that this troubled man obtained many years ago the unlawful union of a second wife, let it suffice that the crime of incest has raged unpunished for a long time. Do not here hesitate as though from fear of divorce, but rightly a lawful separation is judged where a criminal union has existed. If, then, it seems good to both, while they persist in so unhappy an obstinacy, pronounce upon them the mark of excommunication, until by a public profession of penance they wean themselves from the criminal fellowship:
and then, when you show mercy, let them receive the grace of reconciliation, for an example of fear and correction. I have certainly suggested to your sincerity what I believed reasonable, since you thought it worth so much to command it. It belongs to your authority, once the compunction of the erring has been discerned, to temper the order of severity. Yet I reckon that they, if they are truly compunct, will obey the conditions written above.