Should the husband believe his wife's friend in what she said about his wife's actions towards her, and what should he do about it given the lack of tangible evidence?

Harboring ill thoughts about one's wife or other Muslims is forbidden. Therefore, it is not permissible to accuse the wife merely based on something her friend said about her. However, if strong evidence emerges regarding actions that are Islamically prohibited, the husband must be resolute and take appropriate action. Jealousy in a suspicious situation is commendable. If a husband commands his wife to cut off her relationship with a woman, she must obey; otherwise, she is disobedient (nashiz), and disciplining her becomes permissible.