What is the ruling regarding a husband declaring his wife 'as forbidden to him as the back of my mother'?

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Declaring one's wife 'as forbidden to me as the back of my mother' constitutes a clear *Zihar* (in the legal sense). There is scholarly consensus (Ijma) among the people of knowledge that this explicit declaration constitutes *Zihar*. This ruling is established based on the incident involving Khawla, the wife of Aws ibn al-Samit, whose husband made this declaration, and the Messenger of Allah (peace be upon him) ordered him to perform the expiation (*Kaffarah*).