When any of you enters the mosque, let him send peace upon the Prophet and say: Allāhumma iftahli abwāba rahmatik (O Allah, open for me the gates of Your mercy)

The Prophet (ﷺ) guided the Muslim, when entering the mosque, to send peace and blessings upon the Prophet (ﷺ) by saying: Allāhumma salli wa sallim ‘ala Muhammad (O Allah, send Your blessings and peace upon Muhammad), and then to say: Allāhumma iftahli abwāba rahmatik (O Allah, open for me the gates of Your mercy). And when he leaves, he should send peace upon the Prophet and say: Allāhumma i‘simni min ash-shaytān ar-rajīm (O Allah, protect me from the accursed devil).

In another narration by Al-Hākim: And say: Allāhumma ajirni min ash-shaytān ar-rajīm (O Allah, save me from the accursed devil).