Nicæa I: canon V

Concerning those, whether of the clergy or the laity, who have been excommunicated, the sentence is to be respected by the bishops of each province according to the canon which forbids those expelled by some to be admitted by others. But let an inquiry be held to ascertain whether anyone has been expelled from the community because of pettiness or quarrelsomeness or any such ill nature on the part of the bishop. Accordingly, in order that there may be proper opportunity for inquiry into the matter, it is agreed that it would be well for synods to be held each year in each province twice a year, so that these inquiries may be conducted by all the bishops of the province assembled together, and in this way by general consent those who have offended against their own bishop may be recognised by all to be reasonably excommunicated, until all the bishops in common may decide to pronounce a more lenient sentence on these persons. The synods shall be held at the following times: one before Lent, so that, all pettiness being set aside, the gift offered to God may be unblemished; the second after the season of autumn.