Sahih al-Bukhari Book 9, Hadith 55
Allah's Messenger (ﷺ) said, "Whoever could get one rak`a (of the Fajr prayer) before sunrise, he has got the
(morning) prayer and whoever could get one rak`a of the `Asr prayer before sunset, he has got the
(`Asr) prayer."
The believing women covered with their veiling sheets used to attend the Fajr prayer with Allah's Apostle, and after finishing the prayer they would return to their home and nobody could recognize them because of darkness.
Allah's Messenger (ﷺ) said, "Whoever could get one rak`a of a prayer, (in its proper time) he has got the prayer."