(13) باب الدُّعَاءِ عِنْدَ دُخُولِ الْمَسْجِدِ .
It was narrated from Abu Hurairah that:
The Mesenger of Allah said: "When anyone of enters the mosque, let him send peace upon the Prophet, then let him say: 'Allahumma aftahli abwaba rahmatik (O Allah, open to me the gates of Your mercy).' And when he leaves, let him send peace upon the Prophet and say: 'Allahumma- simni minash-shaitanir-rajim (O Allah, protect me from the accursed Shaitan).'"
Reference: Sunan Ibn Majah 773
In-book reference: Book 4, Hadith 39
English translation: Vol. 1, Book 4, Hadith 773