Sunan Abi Dawud 1265
سنن أبي داود#1265SahihNarrated 'Abd Allah b. Sarjas:A man came while the Prophet (ﷺ) was leading the people in the dawn prayer. He prayed the two rak'ahs and then joined the congregational prayer led by the Prophet (ﷺ). When he finished the prayer, the Prophet (ﷺ) said: So-and-so, which was your real prayer, the one you prayed alone or the one offered with us ?
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
Zubair Ali ZaiSahih Muslim (712)
In-book reference: 5:16