Shaykh Saalih Al-Fawzaan was asked:
Q. From that which is known is that it is not permissible to boycott a Muslim for more than three days. Therefore, what is the ruling regarding that which takes place between the husband and the wife of boycotting. Whether he boycotted her to discipline her, or for a reason other than that?
A. If disobedience comes from the wife regarding the right of the husband and he admonished her but she retracts her ill behavior, he can boycott her in the bed. Meaning, he doesn't sleep with her and he doesn't speak to her. Also, he turns his face away from her until she repents. This doesn't contradict the prohibition of the Muslim boycotting his brother for more than three days. That is because this boycotting is restricted to the bed. That which is prohibited is the unrestricted boycotting. Or, it can be said, that which is prohibited is the boycotting which takes place for other than the reason of disobedience. As for the nushooz of the wife, it is considered disobedience which makes boycotting her permissible.
Source: Al-Muntaqaa min Fataawaa Ash-Shaykh Saalih bin Fawzaan 3/251
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