Is it permissible to temporarily boycott a brother to teach him to think before sending hurtful messages, especially after he hurt his sister with a previous message and this has been repeated by him?

The Sharia has prohibited a Muslim from abandoning his brother for more than three nights, except for a legitimate Shar'i excuse. It is permissible to abandon a brother's wife if harm from her is feared, whereas it is not permissible to abandon a brother after he has apologized, as there is no justification for it. It is better to reconcile disputes, for discord is the "shaver" (that shaves away religion), and Muslims should live in harmony and affection, especially relatives.