مَا شَاءَ اللَّهُ تَبَارَكَ اللَّهُ، لَا قُوَّةَ إِلَّا بِاللَّهِ
Transliteration
Ma sha'allahu tabarakallah, la quwwata illa billah
English meaning
What Allah wills. Blessed is Allah. There is no power except with Allah.
When is it recited?
When seeing something admirable — to ward off the evil eye.
Source
Al-Kahf 18/39