Assalaamu alaykum. My question is the following: which of the two is better, praying at night or staying up late at night to seek knowledge? Also, when did the Salaf (pious predecessors) sleep when they remained awake all night? I do not think that they used to waste the blessings of the morning?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.

It is better to do both; perform night prayers as well as engage in seeking knowledge. It was reported that Imaam Ash-Shaafiʻi used to divide his nights into three sections: one third of the night for writing, one-third for performing night prayer, and one-third for sleeping. However, if it is difficult to do both, then seeking knowledge is better and more rewardable. Shaykh Ibn ʻUthaymeen wrote:

"Seeking knowledge is better and more rewardable than any voluntary acts of worship; it is better than performing the Dhuha prayer, night prayer, and all voluntary acts of worship. This is why Abu Hurayrah used to devote his nights to memorizing hadeeth instead of performing night prayer. The Prophet said to him in this regard, "Perform the Witr prayer before you sleep." He approved of his act and did not forbid him from seeking knowledge at night, nor did he order him to devote his night to performing the night prayer instead. This is a very important rule for us to understand. Hence, when the seeker of knowledge engages in discussing, revising, studying, and memorizing the knowledge that he has acquired, then that is better than performing the night prayer and fasting..."

As for your inquiry as to when the Salaf slept since it has been reported that they used to stay up all night devoting themselves to worship, it should be noted that we know of no one of the early Muslim generations who used to stay up all night every night, even if devoted to worship. Rather, they were keen on following the example of the Prophet in this regard, devoting part of the night to performing the night prayer and part of it to sleeping as well. The Prophet reproached the Companions who wanted to exaggerate in carrying out acts of worship. One of those Companions said, "I will not sleep and will perform the night prayer all night long." As the news of that reached the Messenger of Allaah he praised Allaah and then said, "What is the matter with people who say such and such? I pray and I sleep, I fast and I break my fast, and I marry women. Whoever turns away from my Sunnah is not of me (that is, is not one of my followers)." [Ahmad and others]

He also reproached ʻAbdullaah ibn ʻAmr for performing night prayers all night long. He said to him, "O ʻAbdullaah! Have I not been informed that you fast during the day and offer prayers all night?" ʻAbdullaah replied, "Yes, O Messenger of Allaah!" The Prophet said, "Do not do that; fast (some days) and give up fasting (some days); offer prayers and also sleep at night, as your body has a right over you and your eyes have a right over you..."

Moreover, ʻUrwah ibn Az-Zubayr reported that 'Aa'ishah, the wife of the Messenger of Allaah told him that (once) Hawlaa' bint Tuwayt ibn Habeeb ibn Asad ibn ʻAbd Al-ʻUzza passed by her (at the time) when the Messenger of Allaah was with her. 'Aa’ishah said, "It is Hawlaa' bint Tuwayt and they say that she does not sleep at night." Upon this, the Messenger of Allaah said, "(Oh) she does not sleep at all at night! Choose an act that you are capable of doing (continuously). By Allaah, Allaah would not grow weary, but you will grow weary." [Muslim]

An-Nawawi commented on the hadeeth saying:

"The Prophet declared his objection to such an act by expressing his surprise, '(Oh) She does not sleep at all at night!' He clearly disliked such a practice and the way that she burdened herself. This is emphasized by the commentary of Imaam Maalik in his book Al-Muwatta’, which reads, 'The Prophet disliked such an act and his objection was manifest in his facial expressions. This is proof upon which our School of Fiqh relies. According to a group or most of the scholars of our school, it is disliked to perform the night prayer all night long. It has been reported on the authority of some of the righteous predecessors, though, that there is no harm in that.' This view was also one of the reported views of Maalik, as long as the person does not sleep afterwards and then misses the Fajr prayer..." [Sharh Saheeh Muslim]

Rather, some scholars stated that performing the night prayer all night long is not the practice of the righteous predecessors.

The Maaliki scholar Al-Hattaab wrote, "Shaykh Zarrooq said about performing the night prayer all night long that scholars asserted that rendering it a habitual act without having a compelling reason is not the practice of the righteous predecessors..." [Mawaahib Al-Jaleel]

For further information, please refer to fataawa 83503, 85246 and 237589.

Allaah Knows best.