(30) باب مَنْ أَدْرَكَ رَكْعَةً مِنَ الصَّلاَةِ فَقَدْ أَدْرَكَ تِلْكَ الصَّلاَةَ
A'isha reported:
The Messenger of Allah (ﷺ) said: He who finds a prostration before sunset or at dawn (prayer) before the rising (of the sun) he in fact finds that (prayer), and prostration implies a rak'ah. (IT)
Reference (IT): Sahih Muslim 609 (IT)
In-book reference (IT): Book 5, Hadith 208 (IT)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1264 (IT)