وَإِذَا حُيِّيتُم بِتَحِيَّةٍ 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
When you are greeted with a greeting, return one better, or at least return the same. God keeps account of all things.