What should a Muslim say if he is invited for food during the day in Ramaḍān?

Shaykh Muḥammad ibn Hādī al-Madkhalī:

It is as though he is in a non-Islamic land. He should say to him, this is prohibited upon us. We are Muslims and we have this month of fasting, and it is not permissible for us to eat or drink. It is upon him to say this and to clarify to them that this is prohibited upon him during the day time.