Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 1260
Narated By 'Abd Allah b. Sarjas : A man came while the Prophet (pbuh) was leading the people in the dawn prayer. He prayed the two rak'ahs and then joined the congregational prayer led by the Prophet (pbuh). When he finished the prayer, the Prophet (pbuh) said: So and so, which was your real prayer, the one you prayed alone or the one offered with us?