4:86
وَإِذَا حُيِّيتُم بِتَحِيَّةٍ فَحَيُّوا۟ بِأَحْسَنَ مِنْهَآ أَوْ رُدُّوهَآ ۗ إِنَّ ٱللَّهَ كَانَ عَلَىٰ كُلِّ شَىْءٍ حَسِيبًا
wa-idhā ḥuyyītum bitaḥiyyatin faḥayyū bi-aḥsana min'hā aw ruddūhā inna l-laha kāna ʿalā kulli shayin ḥasīban
But [even in battle] when you [believers] are offered a greeting, respond with a better one, or at least return it: God keeps account of everything.
When you are greeted with a greeting, greet in return with what is better than it, or (at least) return it equally. Certainly, Allâh is Ever a Careful Account Taker of all things.