2,203. Whom a Kohein Gadol May/Must Marry

Hilchos Issurei Biah 17:12

If the brother of a Kohein Gadol dies, even if he had only betrothed his wife, the Kohein Gadol may not perform yibum (levirate marriage); rather, he must perform chalitzah. If a woman became his yevama while he was a regular kohein but he was then appointed Kohein Gadol, he may not perform yibum after his appointment. This is so even if he already performed maamar (a pre-yibum declaration) as a regular kohein. However, if he betrothed a widow and was subsequently appointed Kohein Gadol, he should marry her. If she was betrothed but the betrothal was in doubt and the one who betrothed her died, she is considered a doubtful widow.

Hilchos Issurei Biah 17:13

There is a Torah obligation for a Kohein Gadol to marry a virgin “maiden” (naarah); when she reaches adulthood, she becomes prohibited to him. This is based on Leviticus 21:13, “He must marry a virgin woman.” “Woman” – i.e., not a minor; “virgin” – i.e., not yet an adult. This refers to one who has left childhood but has not yet fully matured, which is a naarah. A Kohein Gadol may not be married to two women simultaneously based on the word “woman,” meaning specifically one.