Sunan Ibn Majah 772
سنن ابن ماجه#772SahihIt was narrated that Abu Humaid As-Sa'idi said:"The Messenger of Allah said: 'When anyone of you enters the mosque, let him send peace upon the prophet, then let him say: "Allahummaftah li abwaba rahmatika (O Allah, open to me the gates of Your mercy)." And when he leaves, let him say: "Allahumma inni as'aluka min fadlika. (O Allah, I ask of you from Your bounty)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Zubair Ali ZaiSahih Muslim
In-book reference: 4:38