Sunan Abi Dawud Book 2, Hadith 74
‘Umar b. al-Khattab used to prohibit (men) to enter through the door reserved for women.
This tradition has been reported by 'Umar b. al-Khattab through a different chain of narrators. He narrated it to the same effect and that is more correct.
when any of you enters the mosque he should invoke blessing on the prophet (ﷺ) and then he should say: O Allah, open to me the gates of thy mercy. And when he goes out, he should say: O Allah, I ask thee out of Thine abundance.