Its excellence and merit from the Qur’an: Allah ordered his Messenger to perform salatul tahajjud:
“And some part of the night awake for prayer, a largess for thee. It may be that thy Lord will raise thee to a praised position.”
This order, although it was specifically directed to the Prophet, also refers to all the Muslims since the Prophet is their example and guide in all such matters.
Those who regularly perform the tahajjud prayers are the Righteous and are more deserving of Allah’s bounty and mercy. Allah says: “Lo! Those who keep from evil will dwell amid gardens and water-springs, taking that which their Lord gives them. For, lo, they were doers of good. They used to sleep but little of the night and before the dawning of each day would seek forgiveness.”
Allah praised and complemented the deeds of those who perform the late-night prayers. “The slaves of the Beneficent are they who walk upon the earth in humbleness, and when the ignorant address them, they say: ‘Peace’ and they who spend the night prostrating before their Lord and standing” [ al-Furqan: 63-64 ].
Allah bears witness to their belief in His signs. He says: “Only those believe in Our revelations who, when they are reminded of them, fall down prostrate and hymn the praise of their Lord and they are not shameful: who forsake their beds to cry unto their Lord in fear and hope and spend of what We have bestowed on them. No soul knows what is kept hidden for them of joy as a reward for what they used to do.”
Allah proclaims that those who do not possess these qualities cannot be treated as equal to those who possess them: “Is he who pays adoration in the watches of the night, prostrate and standing, aware of the Hereafter and hoping for the mercy of his Lord equal to a disbeliever? Say: ‘Are those who know equal with those who know not?’ But only men of understanding will pay heed.'”
Fiqh-us-Sunnah Volume 002, Supererogatory Prayer, Fiqh 2.020.
…May Allah give us a better understanding & guide us to accept the truth