صَحِيحُ مُسْلِمٍ
Sahih Muslim 607 a
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
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنِ ابْنِ شِهَابٍ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ مَنْ أَدْرَكَ رَكْعَةً مِنَ الصَّلاَةِ فَقَدْ أَدْرَكَ الصَّلاَةَ .
Abu Huraira reported the Messenger of Allah (ﷺ) as saying: He who finds a rak'ah of the prayer, he in fact finds the prayer.
Sahih Muslim, 607 aSahihصحيح