Arabic
اللَّهُمَّ افْتَحْ لِي أَبْوَابَ رَحْمَتِكَ
Transliteration
Allahummaftah-lī Abwaaba rahmatik.
Translation
O Allah! Open for me the doors of Your mercy.
Guidance
When to recite
Said upon stepping through the door of the Masjid with the right foot first. Applies to entering any mosque.
Source
Sahih Muslim 713
In booklet