The word(s) "obligation" appears 14 time(s) in 12 verse(s) in Quran in Mohsin Khan translation.

(1) O Children of Israel! Remember My Favour which I bestowed upon you, and fulfil (your obligations to) My Covenant (with you) so that I fulfil (My obligations to) your covenant (with Me), and fear none but Me.

(2) O you who believe! Fulfil (your) obligations. Lawful to you (for food) are all the beasts of cattle except that which will be announced to you (herein), game (also) being unlawful when you assume Ihram for Hajj or 'Umrah (pilgrimage). Verily, Allah commands that which He wills.

(3) Freedom from (all) obligations (is declared) from Allah and His Messenger (صلى الله عليه وسلم) to those of the Mushrikun (polytheists, pagans, idolaters, disbelievers in the Oneness of Allah), with whom you made a treaty.

(4) And a declaration from Allah and His Messenger to mankind on the greatest day (the 10th of Dhul-Hijjah - the 12th month of Islamic calendar) that Allah is free from (all) obligations to the Mushrikun (See V.2:105) and so is His Messenger. So if you (Mushrikun ) repent, it is better for you, but if you turn away, then know that you cannot escape (from the Punishment of) Allah. And give tidings (O Muhammad صلى الله عليه وسلم) of a painful torment to those who disbelieve.

(5) That (Manasik- prescribed duties of Hajj is the obligation that mankind owes to Allah), and whoever honours the sacred things of Allah, then that is better for him with his Lord. The cattle are lawful to you, except those (that will be) mentioned to you (as exceptions). So shun the abomination (worshipping) of idol, and shun lying speech (false statements) -

(6) Thus it is [what has been mentioned in the above said Verses (27, 28, 29, 30, 31) is an obligation that mankind owes to Allah] and whosoever honours the Symbols of Allah, then it is truly from the piety of the hearts.

(7) And when the children among you come to puberty, then let them (also) ask for permission, as those senior to them (in age). Thus Allah makes clear His Ayat (Commandments and legal obligations) for you. And Allah is All-Knowing, All-Wise.

(8) On the Day they will see the angels - no glad tidings will there be for the Mujrimun (criminals, disbelievers, polytheists, sinners) that day. And they (angels) will say: "All kinds of glad tidings are forbidden to you," [none will be allowed to enter Paradise except the one who said: La ilaha illallah, "(none has the right to be worshipped but Allah) and acted practically on its legal orders and obligations. See the footnote of V.2:193)].

(9) Among the believers are men who have been true to their covenant with Allah [i.e. they have gone out for Jihad (holy fighting), and showed not their backs to the disbelievers]; of them some have fulfilled their obligations (i.e. have been martyred); and some of them are still waiting, but they have never changed [i.e. they never proved treacherous to their covenant which they concluded with Allah] in the least.

(10) The likeness of those who were entrusted with the (obligation of the) Taurat (Torah) (i.e. to obey its commandments and to practise its laws), but who subsequently failed in those (obligations), is as the likeness of a donkey which carries huge burdens of books (but understands nothing from them). How bad is the example of people who deny the Ayat (proofs, evidence, verses, signs, revelations) of Allah. And Allah guides not the people who are Zalimun (polytheists, wrong-doers, disbelievers).