because no one has the right to alter the law with which Allah sent His Messenger, introduce into Allah’s religion anything He has not authorized, or change the rules governing mosques from what Allah and His Messenger have prescribed. And Allah knows best.

He—may Allah have mercy on him—was asked:

Is it permissible to sleep and talk in the mosque, and to walk in sandals in the areas used for prayer?

He replied:

Sleeping there occasionally is permissible for someone who needs to, such as a stranger or a poor person who has no home. People are, however, told not to make it their regular place for sleeping at night and resting at midday.

Speech that Allah and His Messenger love is good in the mosque. Forbidden speech is even more strictly forbidden there, and disliked speech is likewise more objectionable there. Excessive talk, even about permissible matters, is disliked in the mosque.

Walking in sandals is permissible, just as the Companions used to walk in their sandals in the mosque of the Prophet, may Allah bless him and grant him peace. However, when someone comes to the mosque, he should do as the Messenger of Allah, may Allah bless him and grant him peace, instructed: inspect his sandals, and if there is anything unclean on them, rub them against the earth, for the earth purifies them. And Allah knows best.