Mukhtasar Muslim

Sayyiduna Abu Humayd (or Sayyiduna Abu Usayd) رضي الله عنه narrates that the Messenger of Allah صلى الله عليه وسلم said: When anyone enters the mosque, he should say, "O Allah, open the doors of Your mercy for me," and when he leaves, he should say, "O Allah, I ask You for Your bounty, that is, sustenance and the blessings of this world."