Contrast that with the fragmentation of Islam, everyone following sacred writings but interpreting them in their own way.
Think of the Qur’an as the map to guide us in the journey of life and think of the Sunnah of the Prophet Muhammad (pbuh) as the legend by which to
correctly read this map.
The Prophet (pbuh) did not really need to “explain” every aspect of the Qur’an because his companions as well as his family members used to watch him really closely in practically everything he did.
The hadeeth of Ayesha (ra) states that –
“He (pbuh) was a living Qur’an”… and this means that his way of teaching the others was to act and live according to the Qur’an and then others would watch him and do the same.
Just as we should never be foolish enough to try to read a map without referring to the accompanying legend, then only a fool will attempt to interpret the Qur’an in a way which is different than how the Prophet Muhammad (pbuh) himself followed the teachings of the Qur’an.
And so, it is the Prophet Muhammad (pbuh) who is the ultimate authority on the Qur’an and it is his Sunnah that Muslims refer to in oder to get the most accurate interpretation of the Qur’an possible.
The Prophet Muhammad (pbuh) in his Final Sermon said:
"I leave behind two things, if you hold fast unto them you shall never go astray: the Book of Allah and my Sunnah."
After the Prophet completed this Sermon near the summit of Arafat, the revelation came down:
**“This day have I perfected your religion for you, completed My Grace upon you, and have chosen Islam for you as your religion.” **… (Al Qur’an: Al-Maeda :3)
Bearing in mind that Islam is the finished product to cap all that has been revealed since the dawn of humankind, then to say that what the Creator Himself has deemed a perfect religion would need to be interpreted differently in order to suit the changing times, simply does not make much sense at all.
After all, if the needs and desires of His creations have not changed one iota since 1,400 years ago, then is there a valid reason why the divine Laws that the Creator has commanded His creations to obey back then need to be interpreted differently today?