´It was narrated from Jabir bin 'Abdullah that:` The Messenger of Allah said: "Whoever builds a mosque for the sake of Allah, like a sparrow's nest for Allah or even smaller, Allah will build for him a house in Paradise."
Hadith Referenceسنن ابن ماجه / كتاب المساجد والجماعات / 738
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:إسناده صحيح
1؎: In the hadith, the word «قطاۃ» is mentioned; it refers to a bird that builds its nest in distant forests, and its nest is extremely small. This is an exaggeration to emphasize the smallness of the mosque; otherwise, there is no question of building a mosque as small as a nest, because at the very least, a mosque must have space for three people to perform prayer. The point is that it does not depend on whether the mosque is large or small—if someone, with pure intention, builds even a very small mosque, Allah Ta'ala will still grant him reward, and a house will be built for him in Paradise.
Explanation & Benefits
Maulana Ataullah Sajid
Benefits and Issues: ➊ Qatat is a small bird similar to a pigeon, which makes a small spot on the ground and lays its eggs there. The meaning is that the glad tidings mentioned are not only for the one who builds a large and magnificent mosque, but also for the person who wishes to take even a small part in the construction of a mosque, and is only able to contribute that much—he too will receive the full reward.
➋ With Allah Ta’ala, the importance is not on the outward quantity of deeds, but rather on the sincerity and effort that a person puts forth for any good deed.
Source: Commentary on Sunan Ibn Mājah by Mawlānā ‘Atā’ullāh Sājid, Page: 738