Allah commanded: call adopted children by their fathers' names. Lineage truth is structural; preserving it is justice.

Sūrah al-Aḥzăb verse 5 abolished a deep pre-Islamic practice and replaced it with the Islamic structural protection of biological lineage. The pre-Islamic Arabs frequently adopted children, giving them the adopter's family name; the adopted child became, legally and socially, indistinguishable from biological children. Inheritance rights, marriage prohibitions, and family identity were all affected. The Prophet ﷺ had, before prophethood, adopted Zayd ibn Ḥărithah, a former slave whom Khadījah had given him; the community called him 'Zayd ibn Muḥammad'. After Islam, Zayd was one of the closest Companions, deeply loved by the Prophet ﷺ, eventually martyred as the commander at the Battle of Muʾta. He is the only Companion mentioned by name in the Qurʾan (in Sūrah al-Aḥzăb 33:37). Then the verse 33:5 came. 'adʿūhum li-ăbăʾihim hu wa aqsaṭu ʿinda Allăh; fa-in lam taʿlamū ăbăʾahum fa-ikhwa-nukum fī al-dīn wa-mawălīkum'. Call them (the adopted) by their fathers; that is more just with Allah; and if you do not know their fathers, then they are your brothers in faith and your proteges. The Prophet ﷺ applied the verse to himself first. Zayd, who had been called Zayd ibn Muḥammad for years, was returned to Zayd ibn Ḥărithah, his biological father's name. The Prophet ﷺ, by the verse, was not Zayd's legal father; their relationship continued in love and care, but the lineage-identity was preserved as it truly was. The verse continues: 'and there is no blame on you in what you erred in but [only] what your hearts intended'. Allah forgave the previous practice (calling Zayd as ibn Muḥammad was widespread, not malicious); the prohibition was going forward. Now consider the structural principle the verse establishes. Biological lineage is a divine truth; preserving it is qisṭ, justice. The verse protects several structural realities. First, inheritance. The mawarīth (inheritance shares of the Qurʾan, 4:11-12) are calculated based on biological relationship; adopted-as-biological inheritance would distort the divine allocation. Second, marriage. The maharim categories (Day 198, 4:23) are biological; adopted-as-biological would create false maharim and permit false marriages. Third, identity. The Prophet ﷺ: 'Whoever attributes himself to other than his father knowing he is not his father, Paradise is forbidden to him' (Bukhārī 6766, Muslim 63). The seriousness is named explicitly. The verse 33:5 also provides for the case where the biological father is unknown (the orphan or abandoned child whose lineage cannot be traced). The verse names them as 'your brothers in faith and your proteges (mawălī)'. The terminology preserves the care-relationship while acknowledging the genealogical limitation. This is the basis of classical Islamic kafălah, the caring-sponsorship that provides full love, support, education, and economic provision for the orphan without changing his lineage-identity. The orphan's name remains his biological father's name (or simply 'so-and-so the protege of so-and-so' when the father is unknown). The fiqh provides for inheritance through waṣiyyah (will) up to one-third of the estate to the kafil's kafīl (the cared-for); the rest follows the biological inheritance lines. Now consider the modern application. Many Muslims, in modern adoption legal systems (especially in non-Muslim jurisdictions), are pressured or assume that giving the adopted child their family name is the proper way to integrate them. The Islamic principle is: love the child fully; provide fully; treat as family-of-care; but preserve the biological lineage. Where legal frameworks require certain name-changes for citizenship or legal purposes, the Islamic principle is to preserve the biological lineage in the heart and in honest discourse, while complying with legal requirements that do not contradict sharīʿah essentials. The classical Islamic kafălah is the structural model. Pray today: Allāhumma 'ajʿalnī mim man yarea ḥudūdaka fī al-anhsaŃb wa-yuḥibbu al-yatīmă. O Allah, make me of those who observe Your limits in lineage and who love the orphans. The truth of lineage is preserved; the care for the cared-for is unlimited.