My husband wants a threesome!

My husband (26)and i (24) have been together 6 years and married 2 years. We do have some kinky sex every once and a while but recently my husband has been asking me while we're doing it if I'dlike to have another man inside me. On the one hand it feels weird to think about having sex with another man, even if thats what my husband wants. On the other hand, could be a great time maybe. I dont know how to respond though