Sunan Abi Dawud 555
سنن أبي داود#555Sahih‘Uthman b. ‘Affan reported the Messenger of Allah (may peace be him) as saying; if anyone says the night prayer in congregation, he is like one who keeps vigil (in prayer) till midnight; and he who says both the night and dawn prayer in congregation is like one who keeps vigil (in prayer) the whole night
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Muslim (656)
In-book reference: 2:165