Sunan an-Nasa'i, Volume 1, Book 6, Hadith 554 (DarusSalam) ⓘ
It was narrated from Abu Hurairah that the Messenger of Allah said: "Whoever catches up with a Rak'ah of the prayer, then he has caught up with the prayer."
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، . أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ أَدْرَكَ مِنَ الصَّلاَةِ رَكْعَةً فَقَدْ أَدْرَكَ الصَّلاَةَ " .
also referenced under: Book 6, Hadith 558 (In-Book)