such a person may command certain things although welfare, justice, and truth may lie in doing the opposite; and he may relate matters on the basis of his own ijtihad (personal reasoning) when the reality may be otherwise. Inevitably he will err in some of what he reports concerning theoretical issues and in some of what he prescribes in practical matters, for no one is immune from error except the prophets. Hence it is not obligatory to believe everything any human being says—unless he is a prophet, in which case faith in everything the prophet brings is mandatory.

Allah the Exalted says:

“Say, ‘We believe in Allah, in what has been sent down to us, in what was sent down to Abraham, Ishmael, Isaac, Jacob, and the Tribes; and in what was given to Moses and Jesus and to the prophets from their Lord. We make no distinction between any of them, and to Him we submit.’” (Al-Baqarah 2:136)

And He, the Exalted, says:

“Righteousness is not that you turn your faces toward the east or the west. True righteousness is to believe in Allah, the Last Day, the angels, the Book, and the prophets.” (Al-Baqarah 2:177)

Since matters stand thus, it is known by recurrent, mass transmission that Muhammad declared himself to be a Messenger