Nothing between a servant and his being a Believer...

May Allaah have mercy upon you! Know that there is nothing between a servant and his being a Believer or becoming an unbeliever, except that he denies something which Allaah, the Most High, has sent down, or adds, or takes away anything from the Speech of Allaah, or denies anything which Allaah, the Mighty and Majestic, said, or denies anything said by the Messenger of Allaah, sallAllaahu 'alayhi wa sallam, so fear Allaah. May Allaah have mercy upon you! Beware of your own soul and beware of going into exaggeration in the Religion because it is not from the way of truth at all.

[Sharhus Sunnah, pt.111]