The word(s) "duty" appears 86 time(s) in 79 verse(s) in Quran in Muhammad Habib Shakir translation.

(51) And be careful of (your duty to) Him Who has given you abundance of what you know.

(52) And (We sent) Ibrahim, when he said to his people: Serve Allah and be careful of (your duty to) Him; this is best for you, if you did but know:

(53) Turning to Him, and be careful of (your duty to) Him and keep up prayer and be not of the polytheists

(54) O Prophet! be careful of (your duty to) Allah and do not comply with (the wishes of) the unbelievers and the hypocrites; surely Allah is Knowing, Wise;

(55) And when you said to him to whom Allah had shown favor and to whom you had shown a favor: Keep your wife to yourself and be careful of (your duty to) Allah; and you concealed in your soul what Allah would bring to light, and you feared men, and Allah had a greater right that you should fear Him. But when Zaid had accomplished his want of her, We gave her to you as a wife, so that there should be no difficulty for the believers in respect of the wives of their adopted sons, when they have accomplished their want of them; and Allah's command shall be performed.

(56) There is no blame on them in respect of their fathers, nor their brothers, nor their brothers' sons, nor their sisters' sons nor their own women, nor of what their right hands possess; and be careful of (your duty to) Allah; surely Allah is a witness of all things.

(57) O you who believe! be careful of (your duty to) Allah and speak the right word,

(58) Say: O my servants who believe! be careful of (your duty to) your Lord; for those who do good in this world is good, and Allah's earth is spacious; only the patient will be paid back their reward in full without measure.

(59) They shall have coverings of fire above them and coverings beneath them; with that Allah makes His servants to fear, so be careful of (your duty to) Me, O My servants!

(60) But (as for) those who are careful of (their duty to) their Lord, they shall have high places, above them higher places, built (for them), beneath which flow rivers; (this is) the promise of Allah: Allah will not fail in (His) promise.