`Ali bin Abi Talhah reported that Ibn `Abbas said,

﴿وَأَقِمِ الصَّلَوةَ طَرَفَىِ النَّهَارِ﴾

(And perform the Salah, at the two ends of the day) "This is referring to the morning prayer (Subh) and the evening prayer (Maghrib).'' The same was said by Al-Hasan and `Abdur-Rahman bin Zayd bin Aslam. In one narration reported by Qatadah, Ad-Dahhak and others, Al-Hasan said, "It means the morning prayer (Subh) and the late afternoon prayer (`Asr).'' Mujahid said, "It is the morning prayer at the beginning of the day and the noon prayer (Zuhr) and late afternoon prayer (`Asr) at the end of the day.'' This was also said by Muhammad bin Ka`b Al-Qurazi and Ad-Dahhak in one narration from him.

﴿وَزُلَفاً مِّنَ الَّيْلِ﴾

(and in some hours of the night.) Ibn `Abbas, Mujahid, Al-Hasan and others said, "This means the night prayer (`Isha').'' Ibn Al-Mubarak reported from Mubarak bin Fadalah that Al-Hasan said,

﴿وَزُلَفاً مِّنَ الَّيْلِ﴾

(and in some hours of the night.) "This means the evening (Maghrib) and late night (`Isha') prayers. The Messenger of Allah said,

«هُمَا زُلَفَا اللَّيْلِ: الْمَغْرِبُ وَالْعِشَاء»

(They are the approach of the night: Maghrib and `Isha'.) The same was said by Mujahid, Muhammad bin Ka`b, Qatadah and Ad-Dahhak (that this means the Maghrib and `Isha' prayers). It should be noted that this verse was revealed before the five daily prayers were made obligatory during the night of Isra' (the Prophet's night journey to Jerusalem). At that time there were only two obligatory prayers: a prayer before sunrise and a prayer before sunset. During the late night another prayer (Tahajjud) was also made obligatory upon the Prophet and his nation. Later, this obligation was abrogated for his nation and remained obligatory upon him . Finally, this obligation was abrogated for the Prophet as well, according to one opinion. Allah knows best.