God says
And rise from the sleep and pray during part of the night [as well], as a free offering from thee,*… Q.17:79
Lit., “as a deed beyond that which is incumbent on thee”— i.e., in addition to five obligatory prayers. Hence, the above is not an injunction but a recommendation, although the Prophet, to whom this is addressed, himself invariably spent the greater part of the night in prayer.
…and [true servants of the Most Gracious are they] who remember their Sustainer far into the night, prostrating themselves and standing; -- Q.25:64
Prophet said
“The Lord comes nearest to a servant in the middle of the later half of the night” -- H: Tirmizi. N: Amr-b-‘Abasah
“The most honorable of my followers are those who learn the Qur’an and (get up and) pray (late) at night.” -- H: Baihaqi. N: Ibn Abbas
“Make it a practice to stand at night (for prayer) because it was the practice of the pious before you, and it is a means of expiation of sins, and (also) a preventive measure from committing sin” -- H: Tirmizi. N: Abu Huraira.
