Is it forbidden for a Muslim not to forgive an oppressor who did not initiate seeking forgiveness?

It is forbidden for a Muslim to abandon his brother for more than three nights, and the better of the two is the one who initiates the greeting of peace. Scholars have made an exception for the permissibility of abandoning those who openly commit sins and the people of innovation. A Muslim should break the barrier of estrangement through forgiveness and reconciliation, as this is closer to Allah Almighty. And whoever apologizes to his brother, his apology must be accepted, for whoever does not accept it incurs a sin.