One who boycotts his brother is granted a concession of three days. After those three days it is no longer permissible for him to meet him without giving the greeting of peace—unless the other party is committing a sin that he would abandon if we were to shun him; in that case we boycott him for his own benefit. This is like the Prophet ﷺ boycotting the three men who stayed behind and did not take part in the expedition to Tabuk. Apart from such an exception, the basic rule is that boycotting is forbidden. As for the view reported from some scholars who issue a blanket ruling that anyone who openly commits a sin should be shunned, this requires further examination. Thus, in our understanding, boycotting for up to three days is permissible, while exceeding three days is unlawful unless it serves a legitimate benefit. Allah is the One who grants success.

1568 – Abu Hurayrah (may Allah be pleased with him) reported that the Messenger of Allah ﷺ said: “The gates of Paradise are opened on Monday and Thursday, and every servant who does not associate anything with Allah is forgiven—except a man between whom and his brother there is enmity. It is said, ‘Leave these two until they reconcile, leave these two until they reconcile.’” Narrated by Muslim. In another wording of Muslim: “Deeds are presented every Thursday and Monday,” and he mentioned something similar.

[Explanation]
The compiler, Imam al-Nawawi (may Allah have mercy on him), cited this ḥadīth in his Riyāḍ al-Ṣāliḥīn in the chapter entitled “The Prohibition of Mutual Hatred, Severing Ties, and Turning Away.” It is narrated from Abu Hurayrah (may Allah be pleased with him) that the Prophet ﷺ said: “The gates of Paradise are opened every Monday and Thursday, and every Muslim is forgiven except two men between whom…"