أَعُوذُ بِاللَّهِ الْعَظِيمِ وَبِوَجْهِهِ الْكَرِيمِ وَسُلْطَانِهِ الْقَدِيمِ مِنَ الشَّيْطَانِ الرَّجِيمِ
What this dua means
It seeks Allah's protection the moment you step into His house.
When to read it
Say it with your right foot first as you enter the mosque.
Its virtue
The Prophet said whoever says it, Shaytan says: he is protected from me for the rest of the day.
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