Is a deceased Muslim considered ritually impure, and is it impermissible to bring him into the mosque?

Scholars have agreed upon the purity of a Muslim while alive, but they differed on their purity after death, with two opinions. The correct view is their purity, based on the general statement of the Prophet, peace and blessings be upon him: "Indeed, a believer does not become impure." Al-Shawkani supported the view of purity, citing the aforementioned hadith (definition) and the hadith narrated by Ibn Abbas in Al-Bayhaqi: "Indeed, your deceased dies pure, so it is sufficient for you to wash your hands."

Therefore, there is no harm in bringing the deceased into the mosque and performing the funeral prayer over them therein. Aisha, may Allah be pleased with her, prayed over Sa'd in the mosque, and she narrated that the Prophet, peace and blessings be upon him, only prayed over Ibn Bayda' in the mosque, even though praying over the deceased in a prayer area (musalla) is preferable.