Allah SWT has said in the Holy Quran
[005:003]....This day have I perfected your religion for you and completed MY favour upon you and have chosen for you Islam as religion.Allah swt has perfected this deen for the mankind through Muhammad pbuh. all the messengers who came before him (pbuh) prophecized his (pbuh) coming. Finally, we were blessed to be the ummah of the final messenger pbuh upon who, the final revelation was perfected and completed. The verse mentioned above uses the word "perfected". This word indicates that whatever amendments were needed are done and there is no need for anymore amends in the divine religion, Islam. It does not mean that the previous revelations were not perfect, they indeed were perfect in their own times. But with the completion of deen, the matters are also perfected for the rest of the time.Unfortunately, a part of muslim ummah did not understand this verse and its meaning and started innovations just like the old nations. The old nations were controlled by their priests. Whatever the priests said used to be followed by the common people. Kings used their influence the most to alter the deen for the sake of their ease. This thing continued until islam arrived. Islam made it clear that it is not the religion of priests only and that every man, every person should seek the knowledge of deen by considering it his responsibility. And to not only seek the knowledge but spread it as well. This is one of the reason why we still have the true islam with us. Our book is protected by Allah swt Himself, and our knowledge is still protected by this command.
Allah swt has talked about innovations in deen at many places in Quran, the verses mentioned below say;
[006:140] Losers indeed are those who killed their children foolishly, due to their lack of knowledge, and prohibited what GOD has provided for them, and followed innovations attributed to GOD. They have gone astray; they are not guided.And,
[016:056] They designate for the idols they set up out of ignorance, a share of the provisions we bestow upon them. By GOD, you will be held accountable for your innovations. [046:028] Why then did the idols they set up to bring them closer to GOD fail to help them? Instead, they abandoned them. Such were the false gods they idolized; such were the innovations they fabricated.These verses indicate the following facts about innovations;
1: Innovations are made due to the lack of knowledge of deen. Thus, no matter how much one studies about islam, if he fails to touch the fundamentals of the deen, all that he acquires is half knowledge. Therefore, innovations are result of lack of knowledge.
2: When people innovate, they cross the limits set by Allah swt. This is true. We see that all those innovations which people practice today, they are not only un islamic but also they cross the set limits. Instead of giving food and money to the poors, people spend it in innovations so it true for other blessings and provisions.
3: Whatever is attributed falsely to religion is empty and false. And not only false but when a time of need and help comes, the innovators and their innovations prove to be helpless.
Prophet Muhammad pbuh disliked innovations and said;
Muslim, Book 004, Number 1885:
Jabir b. Abdullah said: When Allah's Messenger (may peace he upon him) delivered the sermon, his eyes became red, his voice rose. and his anger increased so that he was like one giving a warning against the enemy and saying:" The enemy has made a morning attack on you and in the evening too." He would also say:" The last Hour and I have been sent like these two." and he would join his forefinger and middle finger; and would further say:" The best of the speech is embodied in the Book of Allah, and the beet of the guidance is the guidance given by Muhammad. And the most evil affairs are their innovations; and every innovation is error." He would further say:, I am more dear to a Muslim even than his self; and he who left behind property that is for his family. and he who dies under debt or leaves children (in helplessness). the responsibility (of paying his debt and bringing up his children) lies on me."So, the best of the talk is the talk of Quran i.e. the best thing we have been given is Quran. All that is written in it is true and helpful. Similarly, the best guidance and best example for us to follow is prophet Muhammad pbuh. nothing that our beloved prophet said was contradictory to Quran. Whatever was/is attributed falsely to him is a great sin. What our beloved prophet pbuh did not preach and what we cannot find in Quran, it is no where the part of islam.
Muslim ummah needs to stick to Quran and sunnah. Obviously, we need scholarly guidance as well to understand deen better. But we should look for those people who followed these sources and who always speak from Quran and sunnah. We should not look for those who try to reason their perception and relate it with Quran and sunnah.