Sincerity and devotion are comparatively more in worship of the night when compared to worship of the day. For this reason, its excellence also has been described to be greater than the excellence of worship of the day. There is a Hadith in this regard:
Translation: It is narrated on the authority of Hadhrat ‘Abdullah bin Mas’ud (May Allah be well pleased with him), he says that the Holy Prophet (Sallallahu alaihi wa sallam) said: The Salaat offered in the night is superior to the Salaat offered in the day the way charity given in secret is superior to charity given openly. (Mo’jam Kabeer Tabarani, Hadith No. 10229; At Targheeb Wat Tarheeb, Vol. 1, Pg. No. 429)
It is also mentioned in another Hadith that after the Obligatory (Fardh) Salaat, the most excellent is the Salaat of the night:
Translation: It is narrated on the authority of Hadhrat Abu Hurairah (May Allah be well pleased with him), he says that the Holy Prophet (Sallallahu alaihi wa sallam) said: After Ramadhan, the most excellent month is Muharram, the month of Allah and after Obligatory Salaat, the most excellent Salaat is the Salaat of the night. (At Targheeb Fee Fadhaailil A’amaal Li Ibn Shaheen, Hadith No. 558)
2 Raka’at of night – Better than the wealth of the whole world
The Holy Prophet (Sallallahu alaihi wa sallam), who knows the sorrows of the Ummah, has given glad tidings of great reward on small deeds. He has encouraged the Ummah to enliven their nights with worship and prayer and has made clear the importance of doing so:
Translation: It is narrated on the authority of Hadhrat ‘Abdullah bin ‘Umar (May Allah be well pleased with them) that the Holy Prophet (Sallallahu alaihi wa sallam) said: 2 Raka’at that a slave offers in the last part of the night are better than the world and all that it contains. If I didn’t fear of this being hard on my Ummah, then I would certainly have made this 2 Raka’at obligatory on them. (At Targheeb Fee Fadhaailil A’amaal Li Ibn Shaheen, Hadith No. 559)
Thus, it is the custom of the pious to spend the night in worship. By worshipping Almighty Allah in the night, one tires of sins and through its blessings, those who do so will be cured of bodily ailments as well. As mentioned in this Hadith:
Translation: It is narrated on the authority of Hadhrat Bilal (May Allah be well pleased with him) that the Holy Prophet (Sallallahu alaihi wa sallam) said: You make worship of the night compulsory for yourself! As that has been the custom of the pious folk before you. Indeed! Worship of the night is a means of attaining the closeness of Allah Most High, an expiation for sins and an effective means of driving away disease from the body. (Jame’ Tirmidhi, Hadith No. 3895; At Targheeb Wat Tarheeb, Hadith No. 557)