Ahmad ibn Muhammad ibn Isa from Hammad from Hariz from Zurarah from Abu Ja‘far عليه السلام, peace be upon him, who said: I asked Him عليه السلام about what Allah سبحانه وتعالى has made obligatory in terms of prayer. Imam عليه السلام said: "Five prayers during the night and day." So I asked: "Has Allah سبحانه وتعالى named them and clarified them in His Book?" Imam عليه السلام said: "Yes. Allah سبحانه وتعالى, the Mighty and Majestic, said to His Prophet صلى الله عليه وعلى آله وسلم; ‘Establish the prayer from the decline of the sun until the darkness of the night (Surah Al-Isra’ 17:78)’ - And its decline (duluk) is its zenith. And between the decline of the sun and the darkness of the night are four prayers that He عز وجل named, clarified, and set their times. And the darkness of the night is its midpoint. Then Imam عليه السلام said: “And ‘(establish) the recitation of the dawn; indeed, the recitation of the dawn is ever witnessed’, this is (about) the fifth.” And He عز وجل said in that; ‘Establish prayer at the two ends of the day’, and its two ends are Maghrib and Ghadah (fajr, morning). And ‘in the early part of the night’, this is the night prayer (Isha). And He عز وجل said; ‘Guard strictly [five] the prayers, especially the middle prayer’, and that is the Dhuhr prayer, and it was the first prayer that the Messenger of Allah سبحانه وتعالى, may Allah سبحانه وتعالى bless him and his family, prayed. It is the middle of the day and the middle of the two daytime prayers: the morning and the ‘Asr prayers.” And in some recitations it is; ‘Guard strictly the prayers and the middle prayer, the ‘Asr prayer, and stand before Allah سبحانه وتعالى devoutly.’" Imam عليه السلام said: "This verse was revealed on the day of Jumu‘ah while the Messenger of Allah سبحانه وتعالى, may Allah سبحانه وتعالى bless him and his family, was on a journey, and he performed qunut in it and left it as it was in travel and in residence. And He صلى الله عليه وعلى آله وسلم added two rak‘ahs for the resident, and the two rak‘ahs that the Prophet صلى الله عليه وعلى آله وسلم, may Allah سبحانه وتعالى bless him and his family, added on the day of Jumu‘ah for the resident were because of the two sermons with the Imam (of prayer). So whoever prays on the day of Jumu‘ah not in congregation, let him pray it four rak‘ahs like the Dhuhr prayer on the other days."