If he taught others to do something sinful, then he repented from it, will he still carry a burden of sin?
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked a similar question, and he answered:
It appears to me that he does not bear the burden of their sins, because he has repented, and when he repented Allaah forgave him all that has to do with this sin. From this question the danger of bid’ah becomes apparent to us, because if a person follows bid’ah which is a reprehensible innovation – and every bid’ah is a going astray – and other people take that as a custom, they keep this bid’ah alive, based on his actions – may Allaah protect us from that – then he bears the burden of that sin. But if he repents then the apparent meaning of the texts is that the one who repents from sin is like one who did not sin at all.