The third group of rules in the Qur'an are so profound, so well hidden that human power falls short of understanding and deriving them. They cannot be comprehended unless they are explained by Allahu ta'ala. And this fact has been shown and explained only to our Prophet (sall Allahu 'alaihi wa sallam). It has not been explained to anybody else. These rules also are derived from the Qur'an, yet since they have been explained by the Prophet (sall Allahu 'alaihi wa sallam), they are called Sunnat. Concerning the rules of the first and third types, nobody can disagree with the Prophet. All Muslims have to believe and follow them. But on the ahkam-i ijtihadiyya, every mujtahid [He who understands the hidden, symbolic meanings in the Qur'an.] has to follow the rule that he has derived. He cannot follow the rules of other mujtahids. A mujtahid cannot say that another mujtahid has gone wrong, or that he has dissented from the righteous way on account of his ijtihad. For each mujtahid, his own ijtihad is correct and right. Our Prophet used to command his Sahabis whom he sent to distant places to act according to the rules of the Qur'an on matters they would be confronted with, but if unable to find them in the Qur'an, to look them up in hadiths, and if unable to find them there, to act according to their own opinions and ijtihads. He used to forbid them from following others' opinions and ijtihads, even if they were more learned and greater than themselves. No mujtahid, none of the Ashab-i kiram (radi Allahu ta'ala anhum ajmain) has ever discounted as wrong another's ijtihads. They have not uttered such evil terms as 'sinner' or 'aberrant' to those who disagreed with them.