Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The First Ecumenical Council:  The First Council of Nice.: Canon II

Canon II.

Forasmuch as, either from necessity, or through the urgency of individuals, many things have been done contrary to the Ecclesiastical canon, so that men just converted from heathenism to the faith, and who have been instructed but a little while, are straightway brought to the spiritual laver, and as soon as they have been baptized, are advanced to the episcopate or the presbyterate, it has seemed right to us that for the time to come no such thing shall be done.  For to the catechumen himself there is need of time and of a longer trial after baptism.  For the apostolical saying is clear, “Not a novice; lest, being lifted up with pride, he fall into condemnation and the snare of the devil.”  But if, as time goes on, any sensual sin should be found out about the person, and he should be convicted by two or three witnesses, let him cease from the clerical office.  And whoso shall transgress these [enactments] will imperil his own clerical position, as a person who presumes to disobey the great Synod.

Notes.

Ancient Epitome of Canon II.

Those who have come from the heathen shall not be immediately advanced to the presbyterate.  For without a probation of some time a neophyte is of no advantage (κακός).  But if after ordination it be found out that he had sinned previously, let him then be expelled from the clergy.

Hefele.

It may be seen by the very text of this canon, that it was already forbidden to baptize, and to raise to the episcopate or to the priesthood anyone who had only been a catechumen for a short time:  this injunction is in fact contained in the eightieth (seventy-ninth) apostolical canon; and according to that, it would be older than the Council of Nicæa.  There have been, nevertheless, certain cases in which, for urgent reasons, an exception has been made to the rule of the Council of Nicæa—for instance, that of S. Ambrose.  The canon of Nicæa does not seem to allow such an exception, but it might be justified by the apostolical canon, which says, at the close:  “It is not right that any one who has not yet been proved should be a teacher of others, unless by a peculiar divine grace.”  The expression of the canon of Nicæa, ψυχικὸν τι ἁμάρτημα, is not easy to explain:  some render it by the Latin words animale peccatam, believing that the Council has here especially in view sins of the flesh; but as Zonaras has said, all sins are ψυχικὰ ἁμαρτήματα.  We must then understand the passage in question to refer to a capital and very serious offence, as the penalty of deposition annexed to it points out.

These words have also given offence, εἰ δὲ προϊόντος τοῦ χρόνον; that is to say, “It is necessary henceforward,” etc., understanding that it is only those who have been too quickly ordained who are threatened with deposition in case they are guilty of crime; but the canon is framed, and ought to be understood, in a general manner:  it applies to all other clergymen, but it appears also to point out that greater severity should be shown toward those who have been too quickly ordained.

Others have explained the passage in this manner:  “If it shall become known that any one who has been too quickly ordained was guilty before his baptism of any serious offence, he ought to be deposed.”  This is the interpretation given by Gratian, but it must p. 11 be confessed that such a translation does violence to the text.  This is, I believe, the general sense of the canon, and of this passage in particular:  “Henceforward no one shall be baptized or ordained quickly.  As to those already in orders (without any distinction between those who have been ordained in due course and those who have been ordained too quickly), the rule is that they shall be deposed if they commit a serious offence.  Those who are guilty of disobedience to this great Synod, either by allowing themselves to be ordained or even by ordaining others prematurely, are threatened with deposition ipso facto, and for this fault alone.”  We consider, in short, that the last words of the canon may be understood as well of the ordained as of the ordainer.