Nicæa I: canon X

If any have been promoted to ordination through the ignorance of their promoters or even with their connivance, this fact does not prejudice the church's canon; for once discovered they are to be deposed.

Nicæa I: canon IX

If any have been promoted presbyters without examination, and then upon investigation have confessed their sins, and if after their confession men have imposed hands upon such people, being moved to act against the canon, the canon does not admit these people, for the catholic church vindicates only what is above reproach.

Nicæa I: canon II

Since, either through necessity or through the importunate demands of certain individuals, there have been many breaches of the church's canon, with the result that men who have recently come from a pagan life to the faith after a short catechumenate have been admitted at once to the spiritual washing, and at the same time as their baptism have been promoted to the episcopate or the presbyterate, it is agreed that it would be well for nothing of the kind to occur in the future. For a catechumen needs time and further probation after baptism, for the apostle's words are clear: "Not a recent convert, or he may be puffed up and fall into the condemnation and the snare of the devil". But if with the passage of time some sin of sensuality is discovered with regard to the person and he is convicted by two or three witnesses, such a one will be suspended from the clergy. If anyone contravenes these regulations, he will be liable to forfeit his clerical status for acting in defiance of this great synod.

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.