Аль-Ахзаб 33:5

A man does not have two hearts in his chest. This shows that contradictory thinking does not fit in with the scheme of creation. When a man has been given one heart, his thinking should also be one. It cannot be that in one and the same heart, sincerity coexists with hypocrisy, devotion to God with a time-serving mentality, justice with oppression and vanity with modesty. Of the two alternatives, man can have only the God-fearing one, and that is as it should be. This is a matter of principle, and under it are covered the pre-Islamic conventions of divorce (zihar) and adoption. It was the custom among pre-Islamic Arabs that if a man said to his wife, ‘You are like my mother’s back for me’, then his wife was treated as forbidden for him forever, just as his mother was forbidden for him. Similarly, in the matter of an adopted son, they held the belief that he became just like a real son. He was given the same status as a real son in every respect. The Quran abolished this custom completely. It has been made clear in the Quran that it is against the system underlying creation for the status of a real mother to be the same as that of an adoptive mother or the status of an adopted son to be the same as that of a real son. If a man commits an error unknowingly, he is pardonable before God. But, if a man is fully aware of the reality of an affair, and in spite of that he does not desist from wrongdoing, he ceases to be pardonable.