Rejecting Innovation

On the authority of the mother of the faithful, Aisha (ra), who said:

The Messenger of Allah (ﷺ) said, “He who innovates something in this matter of ours (i.e., Islam) that is not of it will have it rejected (by Allah).”

Related by al-Bukhari and Muslim.

In another version in Muslim it reads: “He who does an act which we have not commanded, will have it rejected (by Allah).”