These two rulings were including in an email by salafists from a scholar (that lives in Saudi Arabia and has probably never visited the West) giving advice on how to live in the West.
4. Whenever I see a disbeliever with something nice like a beautiful car is it permissible for me to say, ” Mashallah!” to him?
Answer: Don’t say that to him. The Prophet (peace and blessings be upon him)said,” When you meet them walk in a manner that causes them to walk in a narrower path”.
7.Is it permissible for a Muslim to greet the disbelievers with greetings such as Good morning or Good evening first when meeting?
Answer: No don’t give the disbeliever the greetings first. He should walk pass the disbeliever without giving him the greetings. Perhaps the person with intellect can understand that the reason he’s prohibited from receiving greetings of peace is because he’s a Kafir. A kafir doesn’t believe in the religion of Muhammad (peace and blessings be upon him). By not giving the Kafir the greetings he is pulled to Islam. The Prophet (peace and blessings be upon him) said,” When you meet them don’t give them the greetings first.”
Very practical advice indeed. Bet you’d be a real thrill to be around not speaking to anyone and non-Muslims would want to accept Islam very quickly that way