And We have not made the keepers of the Fire except angels. (74:31)

Almuntakhab Fi Tafsir Alquran Alkarim

(We assigned to no one but the angels the guardianship of the Fire and We stated their number a) to try those infidels unsatisfied desire, b) to assure Ahl AL-Kitab, of the Divine Nature of Muhammads mission, c) to give the faithful reason to consume their wisdom in confidence, d) to give neither party Ahl AL-Kitab and the faithful- an occasion to doubt, e) and to induce the hypocrites, the ill-disposed whose seats of intellect melt away in disease and lassitude as well as the infidels to speak out; and indeed they did. They said: What has Allah meant when He mentioned the Angels number and what does He mean to fulfill?.Thus does Allah mislead whom He pleases and guides whom He will. and no one knows the number of your Creators forces but He, and the description portraying « Saqar » is only a reminder to mankind

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(74:31) We *17 have appointed none but angels as the keepers of the Fire, *18 and We have not made their number but as a trial for the unbelievers *19 so that those who have been endowed with the Book will be convinced *20 and the believers' faith will increase,  *21and neither those who have been endowed with the Book nor the believers will fall into any doubt. As for those in whose hearts there is a sickness *22 as well as the unbelievers, they will say: 'What did Allah aim at by this strange parable?' *23 Thus does Allah let whomsoever He pleases to go astray, and directs whomsoever He pleases *24 to the Right Way. And none knows the hosts of your Lord but He. *25 (And Hell has only been mentioned here) that people may take heed. *26

And We have not made the keepers of the Fire except angels. meaning

*17) The whole passage from here to "none knows the hosts of your Lord but He Himself", is a parenthetical sentence, which has been inserted here to answer an objection of the disbelievers, who had started mocking it when they heard the Holy Prophet (upon whom be peace) say that 19 keepers had been appointed over Hell. Their objection was: "How strange that, on the one hand, we are told that all human beings, from the time of the Prophet Adam till Resurrection, who disbelieved and committed evil, will be cast into Hell. and, on the other, that there will be only 19 keepers, who will administer punishment to the countless numbers of men in such a huge Hell. " This caused a huge laughter among the chiefs of Quraish. Abu Jahl said: "Brothers, are you so powerless that even as many as ten of you at a time will not be able to overpower a single policeman of Hell?" At this a wrestler of the Bani Jumha said: ` Well I will deal with and overpower at least 17 of them by myself; as for the remaining two, you all together can tackle them. " In response these sentences have been inserted as a parenthetical clause.
*18) That is, "It is foolish on your part to compare the angelic powers to human powers. They will be angels, not men, and you cannot imagine what tremendous powers Allah has granted to the angels He has created."
*19) That is, "Although apparently there was no need to mention the number of the keepers of Hell, yet We have mentioned it so that it becomes a trial for every such person who may be concealing any kind of unbelief in his heart. Such a man may be making a great display of his faith but if he conceals even a tinge of the doubt about the Godhead and supreme powers of God, or about Revelation and Prophethood, anywhere in his heart, his disbelief would immediately be exposed as soon as he would hear that only 19 policemen would control countless numbers of the culprits from among the jinn and men in such a huge jail and would also administer punishment to each of them individually. "
*20) Some commentators have explained it thus: "As in the scriptures of the Jews and Christians themselves also the same number of the angels has been mentioned as keepers of Hell, they would be convinced of this thing's being truly from Allah as soon as they heard it." But in our opinion this commentary is not correct for two reasons. First, we have not been able to see anywhere in the existing scriptures of the Jews and Christians in spite of search that the number of the angels appointed over Hell is 19. Second, there are many things in the Qur'an, which also have been mentioned in the scriptures of the Jews and Christians, yet they explain them away, saying that the Prophet Muhammad (upon whom be Allah's peace and blessings) has plagiarized these from their books. For these reasons the correct meaning of this statement in our opinion is: The Holy Prophet Muhammad (upon whom be Allah's peace and blessings) knew fully well that he would be ridiculed as soon as the disbelievers heard that 19 angels had been appointed over Hell, but in spite of this, he presented without the least hesitation and fear publicly before the people what had been revealed to him from Allah, and did not at all mind the jesting and mocking by the people. The pagans of Arabia were unaware of the unique distinction of the Prophets, but the followers of the earlier scriptures were fully aware that the Prophets in every age used to convey to their people intact whatever they received from God, whether it pleased them or displeased them. On this very basis it was to be expected of the Jews and the Christians that they would be convinced of the Prophet Muhammad's truth for only a Prophet could present an apparently strange thing without any hesitation before the people in an environment charged with antagonism and hostility. This also is evident that such a thing was shown by the Holy Prophet on many other occasions. Its most prominent example is the event of the mi'raj (ascension) which he related openly before a general assembly of the disbelievers and did not at all care how his opponents would behave and react after they had heard the story of the wonderful event.
*21) It has been explained at several places in the Qur'an above that on the occasion of every trial when a believer remains steadfast to his faith, and forsaking the way of doubt and denial, disobedience or disloyalty to the faith, adopts the way of faith, obedience and loyalty to it, it increases and strengthens him all the more in faith and resignation (For explanation, see 'Al-Imran: 173, Al-Anfal: 2, At-Taubah: 124125, Al-Ahzab: 22, Al-Fath: 4 and the corresponding E.N.'s).
*22) As "sickness of the heart" in the Qur'an is generally understood to imply hypocrisy, seeing this word here some commentators have expressed the view that this verse was revealed at Madinah, for the hypocrites appeared at Madinah. But this view is not correct for several reasons. In the first place, the assertion itself that there were no hypocrites at Makkah is false, and its false-hood has been exposed in the Introduction to the Surah Al-`Ankabut and in its vv. 1011. Secondly, in our opinion it is not a correct way of writing commentary that in respect of a certain sentence occurring in a particular discourse which was revealed on a particular occasion, under particular circumstances, one should declare that it had been sent down on another occasion but has been inserted here without any relevance. The historical background of this part of Surah AlMuddaththir is fully well known to us from authentic traditions. This was revealed in connection with a particular event of the earliest period of the life at Makkah. The whole context bears full relevance to the event. What could, therefore, be the occasion in this context that this one sentence, if it was revealed many years later at Madinah, should have been inserted here? As for the question what is implied by the disease of the heart here, its answer is that it implies the disease of doubt. Not only in Makkah but in the entire world also there have been, and are, very few such people, who might deny God, Hereafter, Revelation, Prophethood, Heaven. Hell, etc. absolutely. In every age the greater majority by far has been of those people, who have been involved in the doubt whether there is God, or no God, Hereafter or no Hereafter, whether Heaven and Hell really exist, or are mere figments of the imagination, and whether the Messengers did really come and receive Revelation or not. This same doubt has led most people to unbelief, otherwise the number of such people in the world who denied these truths absolutely has never been great. For a person who has any common sense knows that there is no rational ground whatever for denying the possibility of the existence of these things, or of declaring them absolutely impossible.
*23) This dces not mean that they accepted it as Divine word but wondered why Allah had said such a thing. But what they actually meant was: "A discourse which contained such an irrational and impossible thing could not be a Revelation from Allah."
*24) That is, AIlah in this very way sometimes sends down in the course of His Revelations and Commandments such things as become a means of test and trial for the people. It is one and the same thing which a truth-loving, good-natured and right-minded person hears and understanding its right meaning in the right way, adopts the straight path, but which when heard by an obstinate, perverse and wilful wrongdoer, makes him to misconstrue it and make it a new excuse for fleeing from the truth. Since the first man is himself a lover of the truth, Allah grants him guidance, for it is not the way of Allah to lead the seekers after truth forcibly astray; and since the second man himself does not want guidance, but chooses only error for himself, Allah also pushes him on to the way of error and deviation, for it is also not the way of Allah to forcibly pull to the way of the truth him who has an aversion to the truth. (The question of Allah's granting guidance and misguidance has been fully explained at many places for example, see E.N.'s 10. 16, 19, 20 of Al-Baqarah; E.N. 173 of An-Nisa', E.N.'s 17, 28, 90 of AlAn`am, E.N. 13 of Yunus, E.N. 54 of Al-Kahf, E..N. 71 of Al-Qasas)
*25) That is, none knows but Allah what different kinds and how many of the creatures He has created in the universe, what powers He has granted them, and what services He is taking from them. If the man clinging to the tiny globe of the earth seeing the tiny world around himself with his limited sight, is involved in the misunderstanding that the universe of God contains nothing but what he can perceive by his senses or by his instruments, this would only be his own shortsightedness, other wise this universe is so vast and limitless that it is not in the power of man to obtain full knowledge about any of the things here, not to speak of comprehending mentally the concept of all its vastnesses.
*26) "The people may take heed" the people may recover their senses and wake up before they make themselves worthy of Hell and suffer its punishment, and should think of saving themselves from it.
 

And We have not made the keepers of the Fire except angels. meaning in Urdu

ہم نے دوزخ کے یہ کارکن فرشتے بنائے ہیں، اور ان کی تعداد کو کافروں کے لیے فتنہ بنا دیا ہے، تاکہ اہل کتاب کو یقین آ جائے اور ایمان لانے والوں کا ایمان بڑھے، اور اہل کتاب اور مومنین کسی شک میں نہ رہیں، اور دل کے بیمار اور کفار یہ کہیں کہ بھلا اللہ کا اِس عجیب بات سے کیا مطلب ہو سکتا ہے اِس طرح اللہ جسے چاہتا ہے گمراہ کر دیتا ہے اور جسے چاہتا ہے ہدایت بخش دیتا ہے اور تیرے رب کے لشکروں کو خود اُس کے سوا کوئی نہیں جانتا اور اس دوزخ کا ذکر اِس کے سوا کسی غرض کے لیے نہیں کیا گیا ہے کہ لوگوں کو اس سے نصیحت ہو