What is the ruling of Islamic law on the custom of holding a feast for the deceased on the third day, and what is the ruling on a preacher who partakes of this feast and delivers a sermon therein?

Making banquets at funerals and gathering people for them, and bringing reciters, is an innovation (bid‘ah). The Sunnah is for neighbors or relatives to prepare food for the deceased’s family. Attending these banquets is not permissible except for the purpose of denouncing them, because attending them without denouncing encourages innovations, and "whoever increases the number of a people is one of them." The presence of a caller (da‘i) for the purpose of da‘wah (inviting to Islam) and enjoining the fear of Allah and abandoning innovation is legally required. Muslims must abandon these customs that contradict the Sunnah, which burden those afflicted and lead to extravagance.