33:4
Allah has not made for any man two hearts in his (one) body: nor has He made your wives whom ye divorce by Zihar your mothers: nor has He made your adopted sons your sons. Suchis (only) your (manner of) speech by your mouths. But Allah tells (you) the Truth, and He shows the (right) Way.
The passage refers to a pre-Islamic Arabian practice known as ẓihār, in which a husband would declare to his wife, “You are to me like the back of my mother.” Through this statement, the husband effectively withdrew from marital relations with his wife. Although the declaration functioned similarly to an irrevocable divorce, the woman affected by it remained unable to remarry, leaving her in a socially and legally vulnerable position. The Qurʾān addressed this practice by expressing strong disapproval of it, and the custom was later explicitly regulated and abolished in Sūrat al-Mujādilah.
In addition, pre-Islamic Arabian society often treated adopted or foster children as having the same legal status as biological children. This practice carried several legal implications, including the extension of marital prohibitions associated with biological kinship to adopted children. Islamic legal teachings later clarified that adoption, while permissible as a form of care and guardianship, does not establish the same legal lineage as biological parentage. Consequently, the marital restrictions that apply between biological relatives were not extended to adoptive relationships. The Qurʾānic discussion of these issues contributed to redefining family and lineage laws within the emerging Islamic legal framework.
References:
Unal, Ali (2006). The Quran with Annotated Interpretation in Modern English. (surah 8verse 41)