Allāh has not made for a man two hearts in his interior. And He has not made your wives whom you declare unlawful1 your mothers. And He has not made your claimed [i.e., adopted] sons your [true] sons. That is [merely] your saying by your mouths, but Allāh says the truth, and He guides to the [right] way.
Translation: Saheeh International (English)
1 By the expression "You are to me like the back of my mother." Such an oath taken against approaching one's wife was a pre-Islāmic practice declared by Allāh (subḥānahu wa taʿālā) to be a sin requiring expiation as described in 58:3-4.
Just as Allah has not placed two hearts in the chest of any man, as some of them believe, likewise He did not make wives like mothers with respect to being forbidden to marry, and likewise He did not make claimed sons like biological sons, because thihar which is for a man to make his wife unlawful for himself, and likewise, claiming the children of others as one’s own are practices of ignorance which Islam has nullified. That making unlawful through thihar and taking as sons those whose fathers you are not is a statement you repeat with your mouths, which has no reality. The wife is not a mother nor is the claimed son rightfully for the claimant. And Allah says the truth so that His servants practice it, and He guides towards the path of truth.