4:86
وَإِذَا حُيِّيتُم بِتَحِيَّةٍۢ فَحَيُّوا۟ بِأَحْسَنَ مِنْهَآ أَوْ رُدُّوهَآ ۗ إِنَّ ٱللَّهَ كَانَ عَلَىٰ كُلِّ شَىْءٍ حَسِيبًا
Wa izaa huyyeetum bitahiy yatin fahaiyoo bi ahsana minhaaa aw ruddoohaa; innal laaha kaana 'alaa kulli shai'in Haseeba
And when you are greeted with a greeting, greet with a better (greeting) than it or return it; surely Allah takes account of all things.
