V. He distinguishes between laymen who have been raised to the bishoprics and digamous clerks, forgiving the former and not the latter.
Since then either the eager wishes of the people or the intrigues of the ambitious have had so much weight among you that we understand not only laymen, but even husbands of second wives or widows have been promoted to the pastoral office, are there not the clearest reasons for requiring that the churches in which such things have been done should be cleansed by a severer judgment than usual, and that not only the rulers themselves, but also those who ordained them should receive condign punishment?
But there stand on our one hand the gentleness of mercy, on our other the strictness of justice. And because “all the paths of the Lord are loving-kindness and truth,” we are forced according to our loyalty to the Apostolic See so to moderate our opinion as to weigh men's misdeeds in the balance (for of course they are not all of one measure), and to reckon some as to a certain extent pardonable, but others as altogether to be repressed. For they who have either entered into second marriages or joined themselves in wedlock with widows are not allowed to hold the priesthood, either by the apostolic or legal authority: and much more is this the case with him who, as it was reported to us, is the husband of two wives at once, or him who being divorced by his wife is said to have married another, that is, supposing these charges are in your judgment proved.
But the rest, whose preferment only so far incurs blame that they have been chosen to the episcopal function from among the laity, and are not culpable in the matter of their wives, we allow to retain the priesthood upon which they have entered, without prejudice to the statutes of the Apostolic See, and without breaking the rules of the blessed Fathers, whose wholesome ordinance it is that no layman, whatever amount of support he may receive, shall ascend to the first, second, or third rank in the Church until he reach that position by the legitimate steps. For what we now suffer to be to a certain extent venial, cannot hereafter pass unpunished, if any one perpetrates what we altogether forbid: because the forgiveness of a sin does not grant a licence to do wrong, nor will it be right to repeat an offense with impunity which has partly been condoned.
Source: Letters (New Advent)