Muhammad ibn al-Husayn, may Allah have mercy on him, said:

Whoever claims that Allah, Mighty and Majestic, did not speak to Moses has rejected the explicit text of the Quran and disbelieved in Almighty Allah. If one of them says, “Allah Most High created speech in the tree and thereby spoke to Moses,” he is told: “This itself is disbelief, for he claims that speech is created—exalted is Allah, Mighty and Majestic, far above that—and claims that a created being lays claim to lordship. This is among the foulest and most repugnant of statements.”

He is also told: “O heretic! Is it permissible for anyone besides Allah to say, ‘Indeed, I am Allah’?” We seek refuge in Allah from the possibility that one who says this could be a Muslim. Such a person is an unbeliever and must be called to repent. If he repents and renounces his evil doctrine, then that is accepted; otherwise, the ruler is to put him to death. If the ruler neither puts him to death nor calls him to repent, and it becomes known that this is his doctrine, he is to be shunned and not spoken to. He is not to be greeted, prayer is not to be performed behind him, his testimony is not to be accepted, and no Muslim is to give a woman under his guardianship to him in marriage.