A man's family came to make an enquiry (merisik) without letting us know in advance. How should we receive them and answer?

Welcome them warmly, but you do not need to give any answer that day. Serve what you have; guests who arrive unannounced do not expect a big spread. Listen to their intention, take the name and phone number of their representative, and ask a little about the man. Then say politely: ‘Thank you for your kind intention. We need to ask our daughter and discuss it as a family first.’ An answer like this is not a sign of refusal. It gives your daughter time to weigh it up, ask people who know the man, and pray istikharah. Give a rough date by which you will contact them again so no one is left waiting. See proposal (khitbah) guide.