The word(s) "duty" appears 33 time(s) in 31 verse(s) in Quran in Abdullah Yusuf Ali translation.

(11) When some of them said: "Why do ye preach to a people whom Allah will destroy or visit with a terrible punishment?"- said the preachers:" To discharge our duty to your Lord, and perchance they may fear Him."

(12) Those who believed, and adopted exile, and fought for the Faith, with their property and their persons, in the cause of Allah, as well as those who gave (them) asylum and aid,- these are (all) friends and protectors, one of another. As to those who believed but came not into exile, ye owe no duty of protection to them until they come into exile; but if they seek your aid in religion, it is your duty to help them, except against a people with whom ye have a treaty of mutual alliance. And (remember) Allah seeth all that ye do.

(13) Those who believe in Allah and the Last Day ask thee for no exemption from fighting with their goods and persons. And Allah knoweth well those who do their duty.

(14) There is no blame on those who are infirm, or ill, or who find no resources to spend (on the cause), if they are sincere (in duty) to Allah and His Messenger: no ground (of complaint) can there be against such as do right: and Allah is Oft-forgiving, Most Merciful.

(15) Allah turned with favour to the Prophet, the Muhajirs, and the Ansar,- who followed him in a time of distress, after that the hearts of a part of them had nearly swerved (from duty); but He turned to them (also): for He is unto them Most Kind, Most Merciful.

(16) He it is Who enableth you to traverse through land and sea; so that ye even board ships;- they sail with them with a favourable wind, and they rejoice thereat; then comes a stormy wind and the waves come to them from all sides, and they think they are being overwhelmed: they cry unto Allah, sincerely offering (their) duty unto Him saying, "If thou dost deliver us from this, we shall truly show our gratitude!"

(17) He said: "Before any food comes (in due course) to feed either of you, I will surely reveal to you the truth and meaning of this ere it befall you: that is part of the (duty) which my Lord hath taught me. I have (I assure you) abandoned the ways of a people that believe not in Allah and that (even) deny the Hereafter.

(18) Now when they saw no hope of his (yielding), they held a conference in private. The leader among them said: "Know ye not that your father did take an oath from you in Allah's name, and how, before this, ye did fail in your duty with Joseph? Therefore will I not leave this land until my father permits me, or Allah commands me; and He is the best to command.

(19) Whether We shall show thee (within thy life-time) part of what we promised them or take to ourselves thy soul (before it is all accomplished),- thy duty is to make (the Message) reach them: it is our part to call them to account.

(20) He doth send down His angels with inspiration of His Command, to such of His servants as He pleaseth, (saying): "Warn (Man) that there is no god but I: so do your duty unto Me."