The Canons of the Councils of Ancyra, Gangra, Neocæsarea, Antioch and Laodicea, which Canons were Accepted and Received by the Ecumenical Synods 27Canon II.

If a woman shall have married two brothers, let her be cast out [i.e. of communion] until her death. Nevertheless, at the hour of death she may, as an act of mercy, be received to penance, provided she declare that she will break the marriage, should she recover. But if the woman in such a marriage, or the man, die, penance for the survivor shall be very difficult.