First of all, it should be clear that the teachings of Islam have been preserved in their original form. As a result, Allah’s guidance is available without adulteration of any kind. The Qur’an is the revealed book and Word of Allah, which has been in existence for the last fourteen hundred years. It is still available in its original form. Detailed accounts of the life of the Prophet (peace and blessings be upon him) and of his teachings are available in their pristine purity. The sayings and the entire record of the life of the Prophet (peace and blessings be upon him) have been handed down to us with unprecedented precision and authenticity in works of the Hadith and the Sirah (the Prophet’s biography).
Second, the various schools of fiqh and different opinions resulting from ijtihad (independent opinion when there is no clear text on an issue) keep Islam dynamic and vital, able to meet the needs of new eras and circumstances. The basic beliefs and the principles on which laws are made remain unchanged so that Islam is at once both permanent and flexible.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: “The fundamental Islamic sources such as the Qur’an and the core traditions of the Prophet (peace and blessings be upon him) have been fully preserved intact. This can be demonstrated easily by referring to the sound historical methodologies in verifying the sources.
There is a basic distinction between Islam and other religions in this regard: Islam is singularly unique among the world religions in the fact that in order to preserve the sources of their religion, the Muslims invented a scientific methodology based on precise rules for gathering data and verifying them.
As it has been said, “Isnad or documentation is part of Islamic religion, and if it had not been for isnad, everybody would have said whatever he wanted.”
So, there is no comparison between the sources of Islam and those of other religions in this respect, as you will never find anything comparable to the many sciences Muslims invented for this noble task of preserving the sources of Islam. By virtue of such sciences, you can scrutinize and verify every report in the sources.
Thanks to these efforts, the Qur’an as well as the core tradition on which the Islam faith and practices are based, have been fully protected.
The differences among the schools that you have referred to do not concern the major beliefs and practices of Islam, rather they properly belong to the area of furu’ or the details of religion. So, they do not contradict what we have said above. In fact, on a careful study, one would be inclined to assert that such differences among schools of jurisprudence are a true signs of vitality and dynamics of Islam.”