Qur'an 4:86 · An-Nisaa

وَإِذَا حُيِّيتُم بِتَحِيَّةٍۢ فَحَيُّوا۟ بِأَحْسَنَ مِنْهَآ أَوْ رُدُّوهَآ ۗ إِنَّ ٱللَّهَ كَانَ عَلَىٰ كُلِّ شَىْءٍ حَسِيبًا

(86) And when you are greeted with a greeting, greet [in return] with one better than it or [at least] return it [in a like manner]. Indeed Allāh is ever, over all things, an Accountant.