Short Answer
Muslims should treat non-Muslims with kindness as long as they are not hostile to Islam and fighting against them. The Messenger of Allah was kind and friendly with non-Muslims. He accepted the invitation of non-Muslims to eat at his house and invited non-Muslims to his house.
What the Qur’an and Sunnah Say
Allah says, “The believers must not take the disbelievers as allies instead of the believers. And whoever does that has no relation with Allah whatsoever, unless you [do so] as a protective measure [in order to] save yourself from them.” (Qur’an, Aal Imran 3:28)
Allah says, “O you who believe, do not take the Jews and the Christians as allies. They are allies to each other. Whoever takes them as allies is one of them.” (Qur’an, al-Ma’idah 5:5)
Allah also says, “Allah forbids you not, with regards to those who fight you not for (your) Faith nor drive you out of your homes, from dealing kindly and justly with them: for Allah loves those who are just.” (Qur’an, al-Mumtahina, 8)
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Shaykh Mustafa Umar