There are several major proofs, that make it mandatory for us to follow the Sunnah.
The first proof of the importance of the Sunnah, the Prophets all of them, were infallible. All Prophets were infallible when it came to spreading the religion of Allah.
“ O Messenger (Muhammad)! proclaim (the Message) which has been sent down to You from Your Lord. and if You do not, Then You have not conveyed his Message. Allâh will protect You from mankind. Verily, Allâh guides not the people who disbelieve.”
This is evidence that what the Prophet said, was not against the Message of Islam.
“That This is Verily the word of an honoured Messenger (Muhammad Sal-Allaahu ‘alayhe Wa Sallam). It is not the word of a poet, little is that You believe! Nor is it the word of a soothsayer (or a foreteller), little is that You remember! This is the Revelation sent down from the Lord of the ‘Alamin (mankind, jinns and All that exists). And if He (Muhammad Sal-Allaahu ‘alayhe Wa Sallam) had forged a false saying concerning us (Allâh), we surely should have seized Him by his Right Hand (or with power and might),
and Then certainly should have cut off his life artery (Aorta) and none of You could withhold us from (punishing) Him.”
This is evidence that if the Prophet ever said anything against Islam, Allah would have cut off his artery (meaning killing him). This is evidence that anything that comes out of the Prophets mouth is from Allah.
The second proof for Ahadith is, this is the purpose of the Messenger. If Allah had just wanted a book, then the book would have been sent without a messenger. Something, which has never happened. Allah has never spoken to mankind directly, always through a messenger. Allah has always spoken through Prophets and Messengers.
“ we sent no Messenger, but to be obeyed by Allâh’s Leave. if they (hypocrites), when they had been unjust to themselves, had come to You (Muhammad) and begged Allâh’s Forgiveness, and the Messenger had begged Forgiveness for them: indeed, they would have found Allâh All-Forgiving (one who accepts repentance), Most Merciful.”
This is clear proof, that the Messengers have been sent to be obeyed. Prophets of the past have said the same thing:
Prophet Nuh said:
“So fear Allâh, keep Your duty to him, and obey Me.”
Prophet Hud said
“So fear Allâh, keep Your duty to him, and obey Me.”
Prophet Salih said:
“So fear Allâh, keep Your duty to him, and obey Me.”
Prophet Lut said:
“So fear Allâh, keep Your duty to him, and obey Me.”
Prophet Suhaib said:
“So fear Allâh, keep Your duty to him, and obey Me.”
There are about 15 Prophets in the Qur’an saying the very same statement; I just took some of the sayings found in Surah Ash Shuaira.
Another simple proof for the importance following the Sunnah is that the companions of Prophet Muhammad PBUH would follow his Sunnah, and would follow his orders. And Allah would praise them (the companions) in the Qur’an, and he never once reprimanded the companions for following his Sunnah. Yet Allah still reprimanded them in the Qur’an for disobeying the Prophet, but never reprimanded them for obeying him. If they made mistakes, the Qur’an was revealed to guide them, that is why the Sunnah is not misguided.
The fourth proof, are the verses of the Qur’an that prove this point. There are 40+ verses regarding this. I will not be able to quote all of them but I will categorize them.
The first category of verses, are the verses that tell the Muslims to believe in the Messenger of Allah. Very general verses. “Allâh will not leave the believers In the state In which You are now, until He distinguishes the wicked from the good. nor will Allâh disclose to You the secrets of the Ghaib (unseen), but Allâh chooses of his Messengers whom He pleases. so believe In Allâh and his Messengers. and if You believe and fear Allâh, Then for You there is a great reward.”
This is part of Iman(belief), to believe in Prophet Muhammad.
The second categories of verses are the ones that say Prophet Muhammad is the explainer of the Qur’an. Allah sent Prophet Muhammad to explain the Qur’an. If we don’t obey his explanation of the Qur’an, then we are rejecting the Qur’an.
“ with clear signs and Books (We sent the Messengers). and we have also sent down unto You (O Muhammad ) the Reminder and the advice (the Qur’ân), that You may explain clearly to men what is sent down to them, and that they may give thought.”
One of the primary goals of Prophet Muhammad was to explain the Qur’an.
InshAllah Tomorrow or the day after, I will be writing Part 2 of this discussion.