Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Council in Trullo; Often Called The Quinisext Council.: Canon XXVI

Canon XXVI.

If a presbyter has through ignorance contracted an illegal marriage, while he still retains the right to his place, as we have defined in the sacred canons, yet he must abstain from all sacerdotal work.  For it is sufficient if to such an one indulgence is granted.  For he is unfit to bless another who needs to take care of his own wounds, for blessing is the imparting of sanctification.  But how can he impart this to another who does not possess it himself through a sin of ignorance?  Neither then in public nor in private can he bless nor distribute to others the body of Christ, [nor perform any other ministry]; but being content with his seat of honour let him lament to the Lord that his sin of ignorance may be remitted.  For it is manifest that the nefarious marriage must be dissolved, neither can the man have any intercourse with her on account of whom he is deprived of the execution of his priesthood.

Notes.

Ancient Epitome of Canon XXVI.

A priest who has fallen into an illicit marriage and been deposed, may still have his seat, but only when he abstains for the future from his wickedness.

Aristenus.

If any presbyter before his ordination had married a widow, or a harlot, or an actress, or any other woman such as are forbidden, in ignorance, he shall cease from his priesthood but shall still have his place among the presbyters.  But such an illegitimate marriage, on account of which he was deprived of the Sacred Ministry, must be dissolved.

Van Espen.

The sacred canon to which the Synod here refers is number xxvij. of St. Basil in his Canonical Epistle to Amphilochius.