The word(s) "duty" appears 64 time(s) in 61 verse(s) in Quran in Mohsin Khan translation.

(41) O you who believe! Keep your duty to Allah and fear Him, and speak (always) the truth.

(42) You (O Muhammad صلى الله عليه وسلم) are only a warner (i.e. your duty is to convey Allah's Message to mankind but the guidance is Allah's).

(43) "And our duty is only to convey plainly (the Message)."

(44) Say (O Muhammad صلى الله عليه وسلم): "O My slaves who believe (in the Oneness of Allah - Islamic Monotheism), be afraid of your Lord (Allah) and keep your duty to Him. Good is (the reward) for those who do good in this world, and Allah's earth is spacious (so if you cannot worship Allah at a place, then go to another)! Only those who are patient shall receive their reward in full, without reckoning. "

(45) But those who fear their Lord (Allah) and keep their duty to Him, for them are built lofty rooms, one above another under which rivers flow (i.e. Paradise). (This is) the Promise of Allah: and Allah does not fail in (His) Promise.

(46) An Arabic Qur'an, without any crookedness (therein) in order that they may avoid all evil which Allah has ordered them to avoid, fear Him and keep their duty to Him.

(47) And those who kept their duty to their Lord (Al-Muttaqun ) will be led to Paradise in groups, till, when they reach it, and its gates will be opened (before their arrival for their reception) and its keepers will say: Salamun 'Alaikum (peace be upon you)! You have done well, so enter here to abide therein."

(48) And We saved those who believed and used to fear Allah, keep their duty to Him and avoid evil.

(49) But if they turn away (O Muhammad صلى الله عليه و سلم from the Islamic Monotheism, which you have brought to them). We have not sent you (O Muhammad صلى الله عليه و سلم) as a Hafiz (watcher, protector) over them (i.e. to take care of their deeds and to recompense them). Your duty is to convey (the Message). And verily, when We cause man to taste of Mercy from Us, he rejoices thereat; but when some ill befalls them because of the deeds which their hands have sent forth, then verily, man (becomes) ingrate!

(50) Those who avoid great sins (See the Qur'an, Verses: 6:152,153) and Al-Fawahish (illegal sexual intercourse) except the small faults, - verily, your Lord is of Vast Forgiveness. He knows you well when He created you from the earth (Adam), and when you were fetuses in your mothers' wombs. So ascribe not purity to yourselves. He knows best him who fears Allah and keeps his duty to Him [i.e. those who are Al-Muttaqun (the pious. See V.2:2)].