And the extraordinary phenomena that occur at the hands of people who are not prophets do not, according to most scholars, prove that those people are friends of Allah—much less that they are infallible. A friend of Allah is one who dies upon faith, and a mere supernatural feat gives no guarantee that its performer will die in such a state; his condition may yet change. Even when we are certain that someone is a friend of Allah—such as a man about whom the Prophet has testified that he is among the people of Paradise—it is still not obligatory to accept everything he says if his words do not accord with what the prophets have proclaimed. The prophets, peace be upon them, are different: they are protected from error, and it is impossible for any mistake to remain in the message they convey. For that reason Allah has made believing in them mandatory. Whoever disbelieves in even one of them is an unbeliever, and whoever reviles any one of them must be put to death under Islamic law, just as Allah, exalted is He, has said:

“Say, ‘We believe in Allah and in what has been sent down to us, and in what was sent down to Abraham, Ishmael, Isaac, Jacob and the Tribes, and in what Moses and Jesus received, and in what the prophets received from their Lord. We make no distinction between any of them, and to Him we submit.’” [Al-Baqarah 2:136]
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“If they believe in the same as you have believed in, they are rightly guided; but if they turn away, they are only in discord. Allah will suffice you against them, and He is the All-Hearing, the All-Knowing.” [Al-Baqarah 2:137]

And He, exalted is He, says:

“The Messenger has believed in what was sent down to him from his Lord, and so have the believers: each of them believes in Allah, His angels, His Books, and His messengers. They say, ‘We make no distinction between any of His messengers.’ And they say, ‘We hear and obey. Grant us Your forgiveness, our Lord, and to You is the journey’s end.’” [Al-Baqarah 2:285]