Nicæa I: canon I

If anyone in sickness has undergone surgery at the hands of physicians or has been castrated by barbarians, let him remain among the clergy. But if anyone in good health has castrated himself, if he is enrolled among the clergy he should be suspended, and in future no such man should be promoted. But, as it is evident that this refers to those who are responsible for the condition and presume to castrate themselves, so too if any have been made eunuchs by barbarians or by their masters, but have been found worthy, the canon admits such men to the clergy.