دُعَاءُ دُخُولِ الْمَسْجِد
Duʿāʾ Dukhūl al-Masjid — When Entering the Mosque
اللَّهُمَّ افْتَحْ لِي أَبْوَابَ رَحْمَتِكَ
Allāhumma-ftaḥ lī abwāba raḥmatika.
O Allah, open for me the gates of Your mercy.
Abū Usayd reported: The Messenger of Allah ﷺ said: When one of you enters the mosque, let him say, 'O Allah, open for me the gates of Your mercy.' And when he leaves, let him say, 'O Allah, I ask You of Your bounty.'
Source: Ṣaḥīḥ Muslim 713