Abtilis
Canon 18
Overview
This canon prohibits a man from marrying two sisters, or a woman from marrying two brothers, stating that such a union disqualifies the man from clerical office and requires his expulsion from the church community without the possibility of reconciliation alongside the faithful.
1Abṭelis, 18. If a man has married two sisters, or if he has married a woman and she is the sister of his wife, or if a woman has married two brothers, let him not be made a bishop, a presbyter, a deacon, or a reader, nor be raised to the rank of the priesthood. He shall be expelled from the church, and there shall be no reconciliation for him with the believers.