The Messenger of Allah ﷺ said, "Whoever builds a mosque for the sake of Allah, even one as small as a sandgrouse's nesting hollow, Allah will build for him a house in Paradise."
قال رسول الله ﷺ: من بنى الله مسجدا ولو كمفحص قطاة بنى الله له بيتا في الجنة.
Bazzar narrated it in Kashf Astar (401) from Muslim bin Junada bin Salm, who said, Waki narrated to us in Dar, from Sufyan Thawri, from Amash, from Ibrahim, from his father, from Abu Dharr, and he mentioned it. Its chain is sahih.Tabarani also narrated it in Al-Saghir (2/120) via Muammal bin Ismail, who said, Sufyan, meaning Ibn Uyayna, narrated to us, from Amash, similarly. He said, "No one narrated it from Ibn Uyayna except Muammal." End of quote.I say, Muammal bin Ismail Basri is truthful but has a poor memory, so his statement "Sufyan, meaning Ibn Uyayna" is one of his errors. It is actually Sufyan Thawri, as in Waki's narration found in Bazzar. Given this, Muammal bin Ismail was not alone in narrating it, but Waki corroborated him.The hadith has another chain. Ibn Abu Shayba narrated it (310/1) from Yahya bin Adam, who said, Qutba bin Abdul-Aziz narrated to us, from Amash, similarly. Qutba bin Abdul-Aziz bin Siyah Asadi is reliable. Ahmad deemed him reliable and said, "A reliable sheikh," as did Ibn Main, Tirmidhi, Ajli, Ibn Hibban, and others.Ibn Hibban graded the hadith sahih, including it in his Sahih (1610) from Hasan bin Sufyan, from Abu Bakr bin Abu Shayba, similarly.As for Tabarani's statement in Mujam al-Saghir (1382), after narrating it via Ali bin Madini, from Yahya bin Adam, similarly, that "No one narrated it from Qutba except Yahya bin Adam, and Ali bin Madini narrated it alone," this requires scrutiny, since Abu Bakr bin Abu Shayba also narrated it from him.The hadith has yet another chain. Bazzar narrated it (401) from Ahmad bin Yunus, who said, Abu Bakr bin Ayyash narrated to us, from Amash, similarly.Bayhaqi narrated it (2/437) via Abbas bin Muhammad Duri, who said, Ahmad bin Yunus narrated to us. Abbas said, Ahmad bin Yunus said, "It was said to Abu Bakr bin Ayyash, 'People disagree with you on this hadith, they do not narrate it as a raised hadith.'" Abu Bakr bin Ayyash replied, "We heard this from Amash when Amash was a young man."