Dealing with non-muslims

Imam Ahmad narrated with a saheeh isnaad from Abu Moosa that he said: I said to ‘Umar: “I have a Christian scribe.” He said, ‘What is wrong with you, may Allaah doom you?! Have you not heard that Allaah says (interpretation of the meaning): ‘O you who believe! Take not the Jews and the Christians [...]