All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The heresy in Islam means all those acts, which are not proved, from the Prophet Muhammad . The dangers of heresy are very serious. Innovating means legislating something in Islam, which is the absolute right of Allah. Allah Says (what means): {Or have they partners [i.e. other deities] who have ordained for them a religion to which Allah has not consented?} [Quran 42:21]
Besides, the Prophet said: "Whoever introduces into this matter of ours (Islam) that which is not a part of it; it will be rejected.” [Al-Bukhari]
It is also reported that the Prophet said: "You must then follow my Sunnah and that of the rightly-guided Caliphs. Hold on to it and stick fast to it. Avoid newly invented matters, for every newly invented matter is an innovation, and every innovation is an error". [Ahmad, Abu Daawood, At-Tirmithi and Ibn Majah]
All kinds of innovations are nothing but evil. If those who introduce an innovation or practice it do not repent before their death, they will go to Hellfire. The Prophet said: “Of all matters the worst are innovations, and everything new is an innovation, and every innovation is a deviation, and every deviation leads to Hellfire”. [An-Nassa’i] Innovation is a deviation for the one who introduces it and also for the one who follows it. Indeed innovations are more likable to the devil than people disobeying Allah. An innovator believes that he is on the true path so he never repents from his innovations; rather, he believes that those who teach him the Sunnah are deviants.
The popularity of innovations among the Muslims is clear evidence that the Muslims have strayed far from Islam. Allah Says (what means): {And, [moreover] this is My path, which is straight, so follow it; and do not follow [others] ways, for you will be separated from His way. This has He instructed you that you may become righteous.} [Quran 6:153].
Innovations are of two kinds. Some innovations reach the level of disbelief and the one who practices them is no longer Muslim such as the one who claims that the Quran has been changed or that the Quran is not the word of Allah, etc. The other innovations are less serious although they are sins. Thus the one who practices them is considered a Muslim even though he commits sin. An example of the second kind of innovation is fasting the first day of Sha'ban every year, etc.
Working hard to disprove innovations is a communal obligation on the Muslim nation. If someone carries out this job, then other Muslims would be excused from this obligation. If no one carries out the job, all Muslims who are capable to do this job would bear the sin of ignoring this responsibility.
No doubt, two categories of the Muslim Ummah are more responsible for this task than other Muslims, namely the Muslim rulers and the Muslim scholars.
Unfortunately, the majority of the Muslim rulers have given up this task while some of the Muslim scholars are still doing it with a very good impact on the Muslims. Their efforts are blessed and we hope these scholars will continue to fulfill their obligations completely.
Allah knows best.