The word(s) "sincere" appears 18 time(s) in 18 verse(s) in Quran in Mohsin Khan translation.

(1) Say (O Muhammad صلى الله عليه وسلم to the Jews and Christians), "Dispute you with us about Allah while He is our Lord and your Lord? And we are to be rewarded for our deeds and you for your deeds. And we are sincere to Him [in worship and obedience (i.e. we worship Him Alone and none else, and we obey His Orders)]."

(2) (They are) those who are patient, those who are true (in Faith, words, and deeds), and obedient with sincere devotion in worship to Allah. Those who spend [give the Zakat and alms in the Way of Allah] and those who pray and beg Allah's Pardon in the last hours of the night.

(3) 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."

(4) And he [Shaitan (Satan)] swore by Allah to them both (saying): "Verily, I am one of the sincere well-wishers for you both."

(5) Say (O Muhammad صلى الله عليه وسلم): My Lord has commanded justice and (said) that you should face Him only (i.e. worship none but Allah and face the Qiblah, i.e. the Ka'bah at Makkah during prayers) in every place of worship, in prayers (and not to face other false deities and idols), and invoke Him only making your religion sincere to Him (by not joining in worship any partner with Him and with the intention that you are doing your deeds for Allah's sake only). As He brought you (into being) in the beginning, so shall you be brought into being [on the Day of Resurrection in two groups, one as a blessed one (believers), and the other as a wretched one (disbelievers)].

(6) "I convey unto you the Messages of my Lord and give sincere advice to you. And I know from Allah what you know not.

(7) There is no blame on those who are weak or ill or who find no resources to spend [in holy fighting (Jihad)], if they are sincere and true (in duty) to Allah and His Messenger. No ground (of complaint) can there be against the Muhsinun (good-doers - See the footnote of V.9:120). And Allah is Oft-Forgiving, Most Merciful.

(8) To Him belongs all that is in the heavens and (all that is in) the earth and Ad-Din Wasiba is His [(i.e. perpetual sincere obedience to Allah is obligatory). None has the right to be worshipped but Allah)]. Will you then fear any other than Allah?

(9) 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.

(10) 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.