From the Penitential of Finnian of Clonard, on divorce and remarriage and penance:
42. We declare against separating a wife from her husband; but if she has left him, [we declare] that she remain unmarried or be reconciled to her husband according to the Apostle.
43. If a man’s wife commits fornication and cohabits with another man, he ought not to take another wife while his wife is alive.
44. If perchance she is converted to penance, it is becoming to receive her, if she has fully and freely sought this, but he shall not give her a dowry, and she shall go into service to her former husband; as long as he is in the body she shall make amends in the place of a male or a female slave, in all piety and subjection.
45. So also a woman, if she has been sent away by her husband, must not mate with another man so long as her former husband is in the body; but she should wait for him, unmarried, in all patient chastity, in the hope that God may perchance put patience in the heart of her husband. But the penance of these persons is this – that is, of a man or woman who has committed fornication: they shall do penance for an entire year on an allowance of bread and water separately and shall not sleep in the same bed.
This seems quite sensible, in keeping with what the Lord commands against remarrying after divorce.