Mustadrak al-Hakim — Hadith 51

Sayyiduna Abdullah bin Fadalah narrates from his father (Sayyiduna Fadalah al-Laythi (may Allah be pleased with him)), he says: The Messenger of Allah (peace and blessings be upon him) taught me (matters of the religion), and among the things he (peace and blessings be upon him) taught me, he said: "Guard the five prayers." I said: "These are times in which I am busy, so tell me something comprehensive which, if I do it, will suffice for me." He (peace and blessings be upon him) said: "Guard the two 'Asrs ('Asrayn)." The narrator says that this word was not in our language, so I asked: "What are the 'Asrayn?" He (peace and blessings be upon him) said: "A prayer before the sun rises (Fajr) and a prayer before it sets ('Asr)."
Abu Harb bin Abi al-Aswad al-Dili is one of the senior Tabi'in; he narrated from the senior Companions, and his hearing from Sayyiduna Fadalah bin Ubayd al-Laythi is not far-fetched. Moreover, Hushaym bin Bashir is a well-known hafiz of hadith, and Khalid bin Abdullah al-Wasiti is a narrator who possessed a written record (reliable). On the whole, this is just as Imam Muslim recorded in the Book of Faith through Shu'bah from Uthman bin Abdullah bin Mawhab, and after it through Muhammad bin Uthman from his father.