An Nisa, 86 Ayah
4:86
وَإِذَا حُيِّيتُم بِتَحِيَّةٖ فَحَيُّواْ بِأَحۡسَنَ مِنۡهَآ أَوۡ رُدُّوهَآۗ إِنَّ ٱللَّهَ كَانَ عَلَىٰ كُلِّ شَيۡءٍ حَسِيبًا ٨٦
Wa 'Idhā Ĥuyyītum Bitaĥīyatin Faĥayyū Bi'aĥsana Minhā 'Aw Ruddūhā ۗ 'Inna Al-Laha Kāna `Alá Kulli Shay'in Ĥasībāan
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, Allah is ever, over all things, an Accountant.