Musannaf Ibn Abi Shayba 3:781

3158. Shababa narrated to us, he said: Shu'bah narrated to us, from Jabir, from 'Ammar, from Sa'id ibn Jubayr, from Ibn 'Abbas, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever builds a mosque [the size of] the nesting place of a sandgrouse, Allah will build for him a house in Paradise." Abu Bakr said: I found in the book of my father, from al-Humayd ibn Ja'far, from his father, from Mahmud ibn Labid, from 'Uthman, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever builds a mosque, even if it is [the size of] the nesting place of a sandgrouse, Allah will build for him a house in Paradise."