Surah Ad-Dukhan (The Smoke — الدخان) (Ayah 1)

وَقُلْ سَلَامٌ (and say, Salam [ good-bye ]. Then soon they will come to know---Az-Zukhruf 43:89 ^⧉). At the end of the Surah, the same advice has been given to the Holy Prophet t that is always given to every preacher of truth. The gist of the advice is that one may reply to the arguments and doubts of the opponents, but when they start talking ignorantly, foolishly or are involved in hurling abuses, then instead of replying in their language, one should keep quiet. And the instruction to say Salam does not mean that 'Assalamu ` alaikum" is to be said to them, because this salutation is not permissible for any non-Muslim; rather it is an idiomatic expression for parting of ways. As such, the view of those who deduce from this verse that saying "Assalamu 'alaikum" to non-Muslims is permissible does not carry much weight. (Ruh-ul-Ma’ ani).