DUA FOR SAFE FROM CALAMITY ..

The supplication you are referring to is a powerful Prophetic Dua recited to thank Allah for safety, and to seek protection from ever facing the same sickness, trial, or calamity that you witness in others.

The SupplicationArabic:

الْحَمْدُ لِلَّهِ الَّذِي عَافَانِي مِمَّا ابْتَلَاكَ بِهِ وَفَضَّلَنِي عَلَى كَثِيرٍ مِمَّنْ خَلَقَ تَفْضِيلًا

Transliteration:

Alhamdulillahil-ladhi 'afani mim-mab-talaka bihi, wa faddalani 'ala kathirim-mimman khalaqa tafdeela.

English Translation

"All praise is for Allah, Who saved me from that which He tested you with, and Who most certainly favored me over much of His creation."

When and How to Recite ItUpon seeing an afflicted person: 

It is highly recommended to recite this silently to yourself when you see someone suffering from an illness, hardship, or physical disability.

Protect yourself:

 The Prophet Muhammad ﷺ said that whoever sees an afflicted person and recites this Dua will be kept safe from that specific calamity or affliction for as long as they live.

Be respectful: 

Scholars advise saying this quietly so the afflicted person does not hear it and feel sad or grieved.

WALLAHU A'LAM ..