إن ربك يعلم أنك تقوم أدنى من ثلثي الليل ونصفه وثلثه وطائفة (73:20) بالانجليزي

(73:20) (O Prophet), *18 your Lord knows that you sometimes stand up in Prayer nearly two-thirds of the night, and sometimes half or one-third of it,  *19and so does a party of those with you; *20 Allah measures the night and the day. He knows that you cannot keep an accurate count of it, so He has shown mercy to you. So now recite as much of the Qur'an as you can. *21 He knows that there are among you those who are sick and others who are journeying in the land in quest of Allah's bounty, *22 and still others who are fighting in the cause of Allah. *23 So recite as much of the Qur'an as you easily can, and establish Prayer, and pay Zakah, *24 and give Allah a goodly loan. *25 Whatever good you send forth for yourselves, you shall find it with Allah. That is better and its reward is greater. *26 And ask for Allah's forgiveness; surely He is Most Forgiving, Most Compassionate.

Tafseer Abu-al-A'la Maududi

Page 575 English Traditional

*18) About this verse in which reduction has been made in the injunction concerning the Tahajjud Prayer, there are different traditions. Musnad Ahmad, Muslim and Abu Da'ud have related a tradition, on the authority of Hadrat `A'ishah, saying that this second command was sent down one year after the first command, and the standing up in the Prayer at night was made voluntary instead of obligatory. Another tradition which Ibn Jarir and Ibn Abi Hatim have related, again on the authority of Hadrat `A'ishah, says that this command came down 8 months after the first command, and a third tradition which Ibn Abi Hatim has related again from her, says that it came down 16 months later. Abu Da'ud, Ibn Jarir and Ibn Abi Hatim have cited the period of one year from Hadrat `Abdullah bin 'Abbas. But Hadrat Sa'id bin Jubair has stated that it was sent down ten years later. (Ibn Jarir, Ibn Abi Hatim). In our opinion this last view is most sound, for the subject-matter of the first section clearly shows that it was sent down in Makkah and that too in the earliest stage when at the most four years might have passed since the advent of Prophethood. Contrary to this, this second section, .in view of the express evidence of its subject matter, seems to have been revealed at Madinah when fighting had started with the disbelievers and the zakat also had been enjoined as an obligatory duty. On this basis inevitably the two sections should have been sent down at an interval of at least ten years between them.
*19) Although the initial command to the Holy Prophet was to keep standing up in the Prayer for half the. night, or thereabout, it was difficult to compute the tithe precisely in the absorption of the Prayer, especially when there were no watches either to measure time accurately; therefore, sometimes twothirds of the night passed in the prayer and sometimes only one-third of it.
*20) In the initial command only the Holy Prophet (upon whom be peace) was addressed and only he was instructed to stand up in the Prayer by night. But since the Muslims at that time were ardently desirous of following him in everything he did and of earning more and more good and virtues, many of the Companions also performed this Night Prayer regularly.
*21) As the Prayer is prolonged due mainly to a lengthy recital of the Qur'an, it is said: "You may recite as much of the Qur'an as you easily can in the Tahajjud Prayer This would automatically cause the Prayer to be shortened" . Although the words here are apparently in the imperative mood, it is agreed by all that Tahajjud is not an obligatory but a voluntary Prayer. In the Hadith also it has been explained that on an enquiry by a person the Holy Prophet (upon whom be peace) replied: "Five times Prayer in the day and night is obligatory on you. He asked: Is anything besides this also binding on me? The Holy Prophet said: No, unless you may like to offer something of your own accord. " (Bukhari, Muslim). This verse also shows another thing. Just as the bowing (ruku ) and prostration (sajdah.) are obligatory in the Prayer, so is the recital of the Qur'an. For just as Allah at other places has used the words ruku' and sajdah for the prayer, so here He has mentioned recital of the Qur'an, which implies its recital in the Prayer. If somebody objects to this conclusion, saying: When the Tahajjud Prayer itself is voluntary, how can recital of the Qur'an in it be obligatory? The answer is: Even in case of the voluntary Prayer it is incumbent on one to fulfil all the pre-requisites of the Prayer and to perform all its basic elements and obligatory parts. No one can say that in case of the voluntary Prayer, purity of the garments and body, ablutions and concealment of the satar (minimal part of the body to be covered) are not obligatory, and the standing up and sitting and performance of ruku`and sajdah also in it are only voluntary.
*22) Travelling to earn one's living by lawful and permissible methods has been described in many places in the Qur'an as the seeking of Allah's bounty.
*23) Here, the way Allah has made mention of seeking pure livelihood and fighting in the Way of Allah together and declared these two, besides the compulsion on account of illness, as reasons for exemption from the Tahajjud Prayer, or concession in it, shows how meritorious it is in Islam-to earn one's livelihood by lawful methods. In the Hadith, Hadrat `Abdullah bin Mas`ud has reported that the Holy Prophet (upon whom be peace) said: "The person who came to a city of the Muslims with foodgrains and sold it at the rate of the day, will attain to a place nearest to Allah, and then the Holy Prophet recited this very verse." (lbn Marduyah), Hadrat 'Umar once said: "Except for fighting in the way of Allah, the state in which I would love to be overtaken by death, is the state when I am overtaken by it while passing through a mountain pass in search of livelihood and then he recited this very verse." (Baihaqi, Shu ab al-Iman).
*24) Commentators are agreed that this implies observance of the obligatory Prayer five times a day and giving away of the obligatory zakat.
*25) Ibn Zaid says this implies spending one's wealth in the cause of Allah besides the zakat, whether it is in the cause of fighting in the way of Allah, or for helping the needy, or for public utilities, or other good works. The meaning of giving to Allah a good loan has been explained at several places above. See E.N 267 of AI-Baqarah, E.N. 33 of Al-Ma'idah, E.N. 16 of Al-Hadid).
*26) It means: "Whatever you have sent forward for the good of your Hereafter is more beneficial for you than that you withheld in the world and did not spend in any good cause for the pleasure of Allah. According to a Hadith reported by Hadrat 'Abdullah bin Mas`ud the Holy Prophet (upon whom be peace) once asked: "Which of you has a greater love for his own wealth than for the wealth of his heir? The people said: There is none among us, O Messenger of Allah, who would not have greater love for his own wealth than for the wealth of his heir. He said: Consider well what you are saying. The people submitted: This indeed is our considered opinion, O Messenger of Allah. Thereupon the Holy Prophet said: Your own property is only that which you have sent forward (for the good f your Hereafter), and whatever you held back indeed belongs to the heir." (Bukhari. Nasa'i, Musnad Abu Ya`la).