Is it permissible to say to a doctor: "You are a messenger from Allah"? And is it correct to describe Allah Almighty as "the One enthroned upon the Arsh (Throne)"?

Saying to a doctor, "You are a messenger from Allah," meaning that Allah has subjugated him to serve people and treat their apparent illnesses, is a figurative expression (tajawwuz fi al-ibarah) with no harm in it. However, it is better to avoid ambiguous phrases. As for describing Allah with the phrase: "He who is seated upon the Throne," this is impermissible because His attributes are based on divine texts (tawqifiyyah), and this phrase contains ill manners and anthropomorphism (tashbih).