اللَّهُمَّ افْتَحْ لِي أَبْوَابَ رَحْمَتِكَ
Allahumma-ftah li abwaba rahmatik
O Allah, ouvre-moi les portes de Ta miséricorde.
Recite when entering the masjid
The Prophet (PBUH) would say this when entering the masjid, asking Allah to open the doors of His mercy.