Is it permissible to ostracize a colleague at work and not greet him with "peace" (Salam) in order to avoid his troubles, after reconciliation attempts have failed?

It is not permissible for a Muslim to shun his brother for more than three nights. However, shunning is permissible if associating with someone leads to harm, such as a decrease in religious commitment, or harm to oneself or one's worldly affairs. The forbidden shunning is lifted by greeting with salam, and efforts should be made to remove animosity, as it is a cause for delaying forgiveness. Forgiveness is better and increases a servant in honor, and it is a path to attaining Allah's pardon and forgiveness.