Will whoever does not purify himself from major ritual impurity (janabah), nor pray, nor fast, yet believes in the Oneness of Allah, abide eternally in Hellfire?

If one deems the abandonment of ghusl (ritual bath) after janabah (state of ritual impurity requiring ghusl) permissible, then he is an apostate disbeliever after the establishment of proof, because he is denying an obligation upon which there is consensus. However, if he abandons it out of laziness, then his prayer is not valid, and there is a difference of opinion among scholars regarding his disbelief, but he is committing a grave sin, deserving of the most severe warning.