If you see an afflicted person....

The Messenger of Allah (sal Allahu alaihi wa sallam) said: “Whoever unexpectedly comes across a person suffering a calamity, and says, ‘Al-hamdu Lillahil-ladhi ‘afaani mim-mabtalaaka bihi, wa faddalani ‘ala katheerin mimman khalaqa tafdeela,’ will be kept safe from that calamity, no matter what it is.” [Sunan Ibn Majah]

The meaning of this Dua is: “Praise is to Allah Who has kept me safe from that which He has afflicted you with and preferred me over many of those whom He has created.”

If you see anyone suffering any kind of trial, calamity or difficulty, recite this Dua. If you don’t know it in Arabic just say its meaning in whatever language you know. The point is to feel grateful to Allah (subhana wa ta' ala) for keeping you safe and well.

This Dua should be recited quietly to oneself, so that the distressed person does not hear it and feel saddened by it. [Daily Hadith]