Allah commands His Messenger to cease being wrapped up, and this means to be covered during the night. He commands him to get up and stand in prayer to His Lord. This is as Allah says,

﴿تَتَجَافَى جُنُوبُهُمْ عَنِ الْمَضَاجِعِ يَدْعُونَ رَبَّهُمْ خَوْفاً وَطَمَعاً وَمِمَّا رَزَقْنَـهُمْ يُنفِقُونَ ﴾

(Their sides forsake their beds, to invoke their Lord in fear and hope, and they spend out of what We have bestowed on them.) (32:16) Thus, the Prophet did as Allah ordered him, by standing for prayer at night. This was obligatory upon him alone, as Allah said,

﴿وَمِنَ الَّيْلِ فَتَهَجَّدْ بِهِ نَافِلَةً لَّكَ عَسَى أَن يَبْعَثَكَ رَبُّكَ مَقَاماً مَّحْمُودًا ﴾

(And in some parts of the night offer the Salah with it (the Qur'an), as an additional prayer for you. It may be that your Lord will raise you to Maqam Mahmud.) (17:79) Here Allah explains how much prayer he should perform. Allah says,

﴿يأَيُّهَا الْمُزَّمِّلُ - قُمِ الَّيْلَ إِلاَّ قَلِيلاً ﴾

(O you wrapped up! Stand all night, except a little.) Ibn `Abbas, Ad-Dahhak and As-Suddi all said,

﴿يأَيُّهَا الْمُزَّمِّلُ ﴾

(O you wrapped up!) "This means, O you who are asleep.'' Qatadah said, "The one who is wrapped up in his garments.'' Concerning Allah's statement,

﴿نِّصْفَهُ﴾

(Half of it) means, instead of the whole night.

﴿أَوِ انقُصْ مِنْهُ قَلِيلاًأَوْ زِدْ عَلَيْهِ﴾

(A little less than that, or a little more.) meaning, `We have commanded you to stand in prayer for half of the night, either a little more than it or a little less. There is no hardship on you concerning that (slight increase or decrease).