Prematurely Terminating a Nafl Fast by the Instruction of One's Host

Q: Saum-11: Since a host is permitted to prematurely terminate his fast on the instruction of his guest, can a guest prematurely terminate his fast on the instruction of his host?

Answer: Yes. A guest may prematurely terminate his fast on the instruction of his host, but will have to repeat the fast afterwards. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.3