From the Epistle of Gregory III, to Boniface, A.D. 731

Decree V. We have decreed that each one observe his own progeny down to the seventh generation (namely, as to marriages).

This is the first ecclesiastical canon in which it is expressly said that the impediment of consanguinity extends down to the seventh degree. The Fathers of the second Council of Douzy, A.D. 874, attribute this decree, as if taken from the epistle of Gregory the Great to Felix, above, to that same Gregory. But the same Fathers there err not a little in other citations. If you compare this response of Gregory III to Boniface with the response of Gregory II to the same (Response I), the authenticity of each epistle being supposed, you must say one of two things: either that Gregory III abrogated the concession of the former for the Germans, or that he proposed only the general law and narrated what had been decreed in the Synod.

Decree VI. If you are able, teach that it is to be avoided that one whose wife has died ought to be coupled to more than two.

It is counsel concerning the better good, not a precept, that they abstain from third nuptials.