﴿ ۞ إِنَّ رَبَّكَ يَعْلَمُ أَنَّكَ تَقُومُ أَدْنَىٰ مِن ثُلُثَىِ ٱلَّيْلِ وَنِصْفَهُۥ وَثُلُثَهُۥ وَطَآئِفَةٌۭ مِّنَ ٱلَّذِينَ مَعَكَ ۚ وَٱللَّهُ يُقَدِّرُ ٱلَّيْلَ وَٱلنَّهَارَ ۚ عَلِمَ أَن لَّن تُحْصُوهُ فَتَابَ عَلَيْكُمْ ۖ فَٱقْرَءُوا۟ مَا تَيَسَّرَ مِنَ ٱلْقُرْءَانِ ۚ عَلِمَ أَن سَيَكُونُ مِنكُم مَّرْضَىٰ ۙ وَءَاخَرُونَ يَضْرِبُونَ فِى ٱلْأَرْضِ يَبْتَغُونَ مِن فَضْلِ ٱللَّهِ ۙ وَءَاخَرُونَ يُقَٰتِلُونَ فِى سَبِيلِ ٱللَّهِ ۖ فَٱقْرَءُوا۟ مَا تَيَسَّرَ مِنْهُ ۚ وَأَقِيمُوا۟ ٱلصَّلَوٰةَ وَءَاتُوا۟ ٱلزَّكَوٰةَ وَأَقْرِضُوا۟ ٱللَّهَ قَرْضًا حَسَنًۭا ۚ وَمَا تُقَدِّمُوا۟ لِأَنفُسِكُم مِّنْ خَيْرٍۢ تَجِدُوهُ عِندَ ٱللَّهِ هُوَ خَيْرًۭا وَأَعْظَمَ أَجْرًۭا ۚ وَٱسْتَغْفِرُوا۟ ٱللَّهَ ۖ إِنَّ ٱللَّهَ غَفُورٌۭ رَّحِيمٌۢ ﴾

“BEHOLD, [O Prophet,] thy Sustainer knows that thou keepest awake [in prayer] nearly two-thirds of the night, or one-half of it, or a third of it, together with some of those who follow thee. And God who determines the measure of night and day, is aware that you would never grudge it: and therefore He turns towards you in His grace. Recite, then, as much of the Qur’an as you may do with ease. He knows that in time there will be among you sick people, and others who will go about the land in search of God's bounty, and others who will fight in God’s cause. Recite, then, [only] as much of it as you may do with ease, and be constant in prayer, and spend in charity, and [thus] lend unto God a goodly loan: for whatever good deed you may offer up in your own behalf, you shall truly find it with God - yea, better, and richer in reward. And [always] seek God's forgiveness: behold, God is much-forgiving, a dispenser of grace!”

The compulsory duties in religion have been set forth in terms of the common man’s capabilities. But these duties indicate only the minimum of compulsory limits. Beyond these limits there are certain requirements, but these are of a voluntary nature, for example, the offering of the post-midnight prayer (tahajjud) in addition to the five compulsory prayers (fard salat) said at different times throughout the day, or charity in addition to the prescribed alms-giving (zakat), etc. This is the test of a man’s devoutness to see how many more good deeds he performs, thus making himself eligible for greater rewards.