Sahih Muslim 1017e

Some desert Arabs clad in woollen clothes came to the Messenger of Allah (sallallahu alayhi wa sallam). He saw them in sad plight as they had been hard pressed by need. He (the Prophet (sallallahu alayhi wa sallam)) exhorted people to give charity, but they showed some reluctance until (signs) of anger could be seen on his face.

Then a person from the Ansar came with a purse containing silver. Then came another person and then other persons followed them in succession until signs of happiness could be seen on his (sacred) face. Thereupon the Messenger of Allah (sallallahu alayhi wa sallam) said: He who introduced some good practice in Islam which was followed after him (by people) he would be assured of reward like one who followed it, without their rewards being diminished in any respect.

And he who introduced some evil practice in Islam which had been followed subsequently (by others), he would be required to bear the burden like that of one who followed this (evil practice) without their’s being diminished in any respect.