“Their sides forsake their beds, to invoke their Lord in fear and hope, and they spend (charity in Allaah’s Cause) out of what We have bestowed on them” [al-Sajdah 32:16]
The best of prayers after the prescribed prayers is prayer in the depths of the night, and the best of fasting after the month of Ramadaan is fasting the month of Allaah, Muharram.” (reported by Muslim)
The closest that the Lord is to His slave is in the later part of the night, so if you can be one of those who remember Allaah at that time, then do so.” (Reported by al-Tirmidhi)
“The most beloved of prayer to Allaah is the prayer of Dawood, and the most beloved of fasts to Allaah is the fast of Dawood. He used to sleep for half of the night, then get up and pray for a third of the night, then sleep for a sixth of the night, and he used to fast every other day.” (Bukhari+Muslim)
“Whoever recites ten aayaat (verses)in qiyaam will not be recorded as one of the forgetful. Whoever recites a hundred aayaat in qiyaam will be recorded as one of the devout , and whoever prays a thousand aayaat in qiyaam will be recorded as one of the muqantareen (those who pile up good deeds).” (Reported by Abu Dawood)
Al-Fudayl ibn ‘Ayaad said: “I met some people who feel ashamed before Allaah to sleep for too long in the depths of the night. Such a person may be resting on his side, and when he moves, he says to himself, ‘This is not your right. Get up and take your share of the Hereafter”
Al-Hasan said: “We do not know of any deed more difficult than the struggle to stay up at night or to spend money.” It was said to him, “Why do the mutahajjadeen (those who pray Tahajjud at night) have the most beautiful faces?” He said, “Because they spend time alone with the Most Merciful, so He adorns them with some of His light”
He also said “a man commits a sin and so (because of of it) he is deprived of staying up at night”.
Abu’l-Darda’ (may Allaah be pleased with him) said: “Pray two rak’ahs in the darkness of the night for the darkness of the grave.”
Ibn Al mubarak said: ” When the night is completely dark it finds them staying up at night.Fear has chased away their slepp so they stay up, while those who feel secure in this life sleep on”.
man once said to a righteous man, “I am unable to keep on staying up at night; give me a remedy.” The righteous man said, “Do not disobey Him during the day and He will keep you up, between His hands, at night.”
It has been transmitted that Suffian ath-Thawri said, “I was once deprived of staying up at night for five months because of a sin that I had committed.”
Muhammad ibn al-Munkadir said: “There is nothing left of the joys of this life except three: qiyaam al-layl, meeting one’s brothers in faith, and praying in congregation.”
-Purification of the soul (Ibn Rajab/Ibn Qayim)