Iman is an expression of the truth a Muslim recognizes, defined by the Prophet: "Faith is knowledge in the heart, a voicing with the tongue, and an activity with the limbs." The six principles of Iman are mentioned in the Hadith by Gabriel: God, the angels, the scriptures, the prophets, the Last Day and the measuring out. Although there are six principles, they have been grouped by philosophers into three main roots: the tawid, prophecy and the Return. The tawid is the divine unity, the universal message brought by individual prophets to a particular people, at a particular time and place in a particular manner.
The fundamental message of the prophets is tawid and all prophets brought the first Shahadah: "There is no god but I, so worship Me" (21:25). The Koran insists that all prophets be treated equally as they were all sent by the same god with the same guidance and primary message, "To every one of you [messengers] We have appointed a right way and an open road." (5:48) The Koran also states that each prophet was sent to confirm the message of the last. Although the first Shahadah is the same it is in the second Shahadah where there is obvious particularity.
The second Shahadah, Mohammad is His messenger and truths are learned through divine message, pertains to the difference in the prophets that were sent and the particularities in place, time and message detail. There was a different prophet sent to each group of people speaking their individual language. "Every nation has its messenger." (10:47) "We have sent no messenger save with the tongue of his people." (14:4) As well as stating the universality of the message and with the prophets themselves, the Koran also acknowledges the difference in details of their messages. To the Jews but not to Christians God says, "And to the Jewry We have forbidden every beast with claws; and of oxen and sheep We have forbidden them the fat of them, save what their backs carry, or their entrails, or what is mingled with the bone.
