The Messenger of Allah ﷺ said, "Whoever catches one rakah of the Asr prayer before the sun sets has caught it, and whoever catches one rakah of the Fajr prayer before the sun rises has caught it."
حدثنا عبد الرزاق حدثنا معمر عن الزهري عن أبي سلمة
أن رسول الله ﷺ قال من أدرك من العصر ركعة قبل أن تغرب الشمس فقد أدركها ومن أدركها من الصبح قبل أن تطلع الشمس فقد أدركها
Its chain of transmission is sahih. It is a repetition of 7451, with similar wording, and we have already pointed out some of its narrations there. Nasai (1:90) narrated something similar in meaning from this route, through Mutamir, who is Ibn Sulayman, from Mamar, with this chain of transmission.As for the wording "whoever catches a rakat of the dawn prayer," in manuscript H it reads "whoever catches it of the dawn prayer," and we have kept what is established in manuscript K. As for manuscript M, it read "whoever catches of the dawn prayer," omitting "rakat" and omitting the pronoun. Then the pronoun "it" was added afterward in a different hand, attached to the letter kaf in "catches."