The word(s) "observe" appears 49 time(s) in 47 verse(s) in Quran in Muhammad Pickthal translation.

(11) O ye who believe! observe your duty to Allah, and give up what remaineth (due to you) from usury, if ye are (in truth) believers.

(12) O ye who believe! When ye contract a debt for a fixed term, record it in writing. Let a scribe record it in writing between you in (terms of) equity. No scribe should refuse to write as Allah hath taught him, so let him write, and let him who incurreth the debt dictate, and let him observe his duty to Allah his Lord, and diminish naught thereof. But if he who oweth the debt is of low understanding, or weak, or unable himself to dictate, then let the guardian of his interests dictate in (terms of) equity. And call to witness, from among your men, two witnesses. And if two men be not (at hand) then a man and two women, of such as ye approve as witnesses, so that if the one erreth (through forgetfulness) the other will remember. And the witnesses must not refuse when they are summoned. Be not averse to writing down (the contract) whether it be small or great, with (record of) the term thereof. That is more equitable in the sight of Allah and more sure for testimony, and the best way of avoiding doubt between you; save only in the case when it is actual merchandise which ye transfer among yourselves from hand to hand. In that case it is no sin for you if ye write it not. And have witnesses when ye sell one to another, and let no harm be done to scribe or witness. If ye do (harm to them) lo! it is a sin in you. observe your duty to Allah. Allah is teaching you. And Allah is knower of all things.

(13) If ye be on a journey and cannot find a scribe, then a pledge in hand (shall suffice). And if one of you entrusteth to another let him who is trusted deliver up that which is entrusted to him (according to the pact between them) and let him observe his duty to Allah his Lord. Hide not testimony. He who hideth it, verily his heart is sinful. Allah is Aware of what ye do.

(14) O ye who believe! observe your duty to Allah with right observance, and die not save as those who have surrendered (unto Him)

(15) Allah had already given you the victory at Badr, when ye were contemptible. So observe your duty to Allah in order that ye may be thankful.

(16) O ye who believe! Devour not usury, doubling and quadrupling (the sum lent). observe your duty to Allah, that ye may be successful.

(17) O ye who believe! Endure, outdo all others in endurance, be ready, and observe your duty to Allah, in order that ye may succeed.

(18) When ye have performed the act of worship, remember Allah, standing, sitting and reclining. And when ye are in safety, observe proper worship. Worship at fixed times hath been enjoined on the believers.

(19) They ask thee (O Muhammad) what is made lawful for them. Say: (all) good things are made lawful for you. And those beasts and birds of prey which ye have trained as hounds are trained, ye teach them that which Allah taught you; so eat of that which they catch for you and mention Allah's name upon it, and observe your duty to Allah. Lo! Allah is swift to take account.

(20) O ye who believe! Be steadfast witnesses for Allah in equity, and let not hatred of any people seduce you that ye deal not justly. Deal justly, that is nearer to your duty. observe your duty to Allah. Lo! Allah is Informed of what ye do.