Is it proper to greet a non-Muslim with "As-Salāmu Alaykum"?

It is generally not proper to initiate the greeting "As-Salāmu Alaykum" with non-Muslims, but it is acceptable to respond to their greetings. The Qur'an advises believers on how to handle greetings in a respectful manner. In Surah An-Nisaa, it is stated: When ye are greeted with a greeting, greet ye with a better than it or return it. 4:86. This verse emphasizes the importance of responding to greetings appropriately.

When it comes to responding to the greetings of non-Muslims, the Prophet Muhammad ﷺ provided specific guidance. In a narration from Sahih al-Bukhari, it is reported that A Jew passed by Allah's Apostle and said, 'As-Samu 'Alaika.' Allah's Apostle said in reply, 'We 'Alaika.' Allah's Apostle then said to his companions, 'Do you know what he (the Jew) has said? He said, 'As-Samu 'Alaika.' They said, 'O Allah's Apostle! Shall we kill him?' The Prophet said, 'No. When the people of the Book greet you, say: 'Wa 'Alaikum.' Sahih al-Bukhari 84:60. This narration shows that when Jews or Christians greet Muslims, the recommended response is to say "Wa 'Alaikum," meaning "And on you."

Furthermore, Al-Kafi, a Shia hadith collection, also addresses this matter, stating: When a Jew, Christian or a pagan greets you with peace just say, 'Alayka' meaning, 'the same to you.' Al-Kafi 11:3642. This reinforces the idea that while Muslims should not initiate the greeting of peace with non-Muslims, they should reciprocate respectfully.

Additionally, Sahih al-Bukhari records: If the people of the Scripture greet you, then you should say (in reply), 'Wa'alaikum (And on you).' Sahih al-Bukhari 74:275. This further clarifies the response that is appropriate when greeted by people of other faiths.

Thus, while it is not proper to initiate "As-Salāmu Alaykum" with non-Muslims, responding with "Wa 'Alaikum" or "Alayka" is acceptable and encouraged.