It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever participates in building a mosque for Allah—even if it is as small as a bird’s nest where a sandgrouse lays its eggs—Allah will build for him a house in Paradise."
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 2157
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لضعف جابر الجعفي.