صَحِيحُ مُسْلِمٍ
Sahih Muslim 608 d
The Book of Mosques and Places of Prayer
The one who catches up with a rak`ah of the prayer, he has caught up with that prayer
وَحَدَّثَنَاهُ عَبْدُ الأَعْلَى بْنُ حَمَّادٍ، حَدَّثَنَا مُعْتَمِرٌ، قَالَ سَمِعْتُ مَعْمَرًا، بِهَذَا الإِسْنَادِ .
This hadith has been reported by Ma'mar with another chain of transmitters.
Sahih Muslim, 608 dSahihصحيح