‘Abd Allaah (bin Masud) said “I asked Apostle of Allaah(ﷺ) which sin is the gravest?” He replied “That you associate someone with Allaah, while He has created you”. I again asked “Which then?” He replied “That you commit adultery with the wife of your neighbor.” Allaah then revealed the following Qur’anic verse in support of the statement of the Prophet (ﷺ) “Those who invoke not with Allaah any other god nor slay such life as Allaah has made sacred except for just cause nor commit fornication.”