“Sincerity” is a Word closely connected with the Qur'an. We could not know what sincerity is if we do not know the Qur'an. Sincerity means a person's not applying any pressure on his brain and thinking on the side of God in everything; it means his never expostulating on God- may God forbid, his never being troubled by God or never rebelling against God- may God forbid. - Harun Yahya