898. If you see someone smiling
أَضْحَكَ اللَّهُ سِنَّكَ
Adh’haka allahu sinnak
Translation
May Allah keep you happy always.
ReferenceBukhari: 3294
Related Duas:
If someone does a good job for you
Protection from the Dajjal
Dua to one who says 'May Allah bless you'
For the one who asks Allah to forgive your sins
Seeking refuge from four things
Etiquette of praising a fellow Muslim
For the one that have been praised
If anyone likes you for the sake of Allah
Forbiddance of ascribing things to omens
For one you have insulted