What is the ruling on a Christian guardian appointing a Muslim to marry off his daughter to a Muslim man, due to his inability to attend the عقد (marriage contract), and with no man of his own religion present at the assembly? And is it permissible for him to appoint the mosque's sheikh by phone?

Marriage is not valid except with a guardian (wali) and two just witnesses. The majority of scholars stipulate that the two witnesses must be Muslim. As for the guardian, he must be of the same religion as the woman he is overseeing.

If a Christian guardian wishes to appoint a Muslim as his agent to officiate his daughter's marriage, jurists have differed on this matter: - Maliki and Hanbali schools: This is not valid. The agent must be of the same religion as the guardian. - Shafi'i school: It is permissible for a People of the Book (Kitabi) to appoint a Muslim as his agent in marrying off his ward. Therefore, the marriage is valid according to the Shafi'i madhhab (definition).