Reference: http://www.alfawzan.af.org.sa/node/14788
Question: What is the ruling regarding accepting the wedding invitation of the Rawaafidh (Shee’ah)? And is their meat halaal for us?
Response: [Regarding] their meat, [then] no, it is not [halaal for us]; as for their invitation, then if it is anticipated they will repent [from their beliefs], then accepting their invitation would be an encouragement for them to repent [in shaa.-Allaah]. And if they are neighbours, then the neighbour already has a right [over you] if they invite you.
