Is belief in the effect of the evil eye upon the envied a religious matter that is obligatory to believe, or a worldly issue, and what is the ruling on one who denies it?

Whoever denies the effect of the evil eye, while being aware of the hadiths that mention it, is a disobedient person (fasiq) and not an apostate, because he has not denied something that is known by necessity in the religion, nor something established by a definitive proof. However, whoever denies it with the intention of disbelieving the Prophet, peace and blessings be upon him, is considered a disbeliever (kafir) and an apostate.