The word(s) "sincerely" appears 9 time(s) in 9 verse(s) in Quran in Mohsin Khan translation.

(1) Then whoever disputes with you concerning him ['Îsa (Jesus)] after (all this) knowledge that has come to you [i.e. 'Îsa (Jesus) being a slave of Allah, and having no share in Divinity], say: (O Muhammad صلى الله عليه وسلم) "Come, let us call our sons and your sons, our women and your women, ourselves and yourselves - then we pray and invoke (sincerely) the Curse of Allah upon those who lie."

(2) And when harm touches men, they cry sincerely only to their Lord (Allah), turning to Him in repentance; but when He gives them a taste of His Mercy, behold, a party of them associates partners in worship with their Lord.

(3) Verily We have sent down the Book to you (O Muhammad صلى الله عليه وسلم) in truth: So worship Allah (Alone) by doing religious deeds sincerely for Allah's sake only.

(4) Say (O Muhammad صلى الله عليه وسلم): "Verily I am commanded to worship Allah (Alone) by obeying Him and doing religious deeds sincerely for His sake only.

(5) Say (O Muhammad صلى الله عليه وسلم): "Allah Alone I worship by doing religious deeds sincerely for His sake only (and not to show off, and not to set up rivals with Him in worship.)"

(6) So, call you (O Muhammad صلى الله عليه وسلم and the believers) upon (or invoke) Allah making (your) worship pure for Him (Alone) (by worshipping none but Him and by doing religious deeds sincerely for Allah's sake only and not to show off and not to set up rivals with Him in worship), however much the disbelievers (in the Oneness of Allah) may hate (it).

(7) He is the Ever Living, La ilaha illa Huwa (none has the right to be worshipped but He); so invoke Him making your worship pure for Him Alone (by worshipping Him Alone, and none else, and by doing righteous deeds sincerely for Allah's sake only, and not to show off, and not setting up rivals with Him in worship). All the praises and thanks be to Allah, the Lord of the 'Alamin (mankind, jinn and all that exists).

(8) Those who deny the Book (this Qur'an), and that with which We sent Our Messengers (i.e. to worship none but Allah Alone sincerely, and to reject all false deities and to confess resurrection after the death for recompense) they will come to know (when they will be cast into the Fire of Hell).

(9) It may be if he divorced you (all) that his Lord will give him instead of you, wives better than you - Muslims (who submit to Allah), believers, obedient (to Allah), turning to Allah in repentance, worshipping Allah sincerely, given to fasting or emigrants (for Allah's sake), previously married and virgins.