The word(s) "must" appears 38 time(s) in 31 verse(s) in Quran in Mohsin Khan translation.

(21) For every nation We have ordained religious ceremonies [e.g. slaughtering of the cattle during the three days of stay at Mina (Makkah) during the Hajj (pilgrimage)] which they must follow; so let them (the pagans) not dispute with you on the matter (i.e. to eat of the cattle which you slaughter, and not to eat of the cattle which Allah kills by its natural death), but invite them to your Lord. Verily you (O Muhammad صلى الله عليه وسلم) indeed are on the (true) straight guidance (i.e. the true religion of Islamic Monotheism).

(22) For them there will be therein all that they desire, and they will abide (there forever). It is a promise binding upon your Lord that must be fulfilled.

(23) "O my son! If it be (anything) equal to the weight of a grain of mustard seed, and though it be in a rock, or in the heavens or in the earth, Allah will bring it forth. Verily, Allah is Subtle (in bringing out that grain), Well-Aware (of its place).

(24) And indeed they had already made a covenant with Allah not to turn their backs, and a covenant with Allah must be answered for.

(25) And (remember) when you said to him (Zaid bin Harithah رضي الله عنه - the freed-slave of the Prophet صلى الله عليه وسلم) on whom Allah has bestowed Grace (by guiding him to Islam) and you (O Muhammad صلى الله عليه وسلم too) have done favour (by manumitting him): "Keep your wife to yourself, and fear Allah." But you did hide in yourself (i.e. what Allah has already made known to you that He will give her to you in marriage) that which Allah will make manifest, you did fear the people (i.e., their saying that Muhammad صلى الله عليه وسلم married the divorced wife of his manumitted slave) whereas Allah had a better right that you should fear Him. So when Zaid had accomplished his desire from her (i.e. divorced her), We gave her to you in marriage, so that (in future) there may be no difficulty to the believers in respect of (the marriage of) the wives of their adopted sons when the latter have no desire to keep them (i.e. they have divorced them). And Allah's Command must be fulfilled.

(26) And what We have revealed to you (O Muhammad صلى الله عليه وسلم), of the Book (the Qur'an), it is the (very) truth [that you (Muhammad صلى الله عليه وسلم) and your followers must act on its instructions], confirming that which was (revealed) before it. Verily! Allah is indeed All-Aware, and All-Seer of His slaves.

(27) And verily, if you ask them: "Who created the heavens and the earth?" Surely they will say: "Allah (has created them)." Say: "Tell me then, the things that you invoke besides Allah - if Allah intended some harm for me, could they remove His harm? Or if He (Allah) intended some mercy for me, could they withhold His Mercy?" Say: "Sufficient for me is Allah; in Him those who trust (i.e. believers) must put their trust. "

(28) And he who finds not (the money for freeing a slave) must fast two successive months before they both touch each other. And he who is unable to do so, should feed sixty Miskins (poor). That is in order that you may have perfect Faith in Allah and His Messenger. These are the limits set by Allah. And for disbelievers, there is a painful torment.

(29) Surely, what you are promised must come to pass.

(30) And listens to and obeys its Lord - and it must do so.