Hadith 5 from An-Nawawi
BismiLlah Al Rahman Al Rahim,
It is narrated on the authority of the Mother of the Believers, Umm ‘Abdullah ‘Aishah, radiyallahu ‘anha, that the Messenger of Allah, sallallahu ‘alayhi wasallam, said:
“Whosoever introduces into this affair of ours (i.e. into Islam) something that does not belong to it, it is to be rejected.”
[Al-Bukhari & Muslim]
According to the version in Muslim, (it reads): “Whosoever works a work which has for it no command of ours is to be rejected.”
This is a great rule. Any matter that was not part of our religion is not accepted.
Writing the Qur’an (during Abu Bakr’s (may Allah be pleased with him) caliphate) was an innovation
The four madhabs (schools) were an innovation
BUT they were accepted since they were based on the Qur’an and Hadith.
This hadith is a skeleton for our extended deeds (like praying tarawih during Ramadan at the masjid every day was introduced by ‘Umar (may Allah be pleased with him).
When someone takes an innovation and makes it an obligation, it is not accepted.