Nasa'i 3359 records the canonical framework of forbidden marriage degrees in Islamic law. The Quranic mandate (Q 4:23) establishes the prohibited categories. The hadith elaborates additional rules including foster-relations (radhāʿa, treated under entry m08 for adult breastfeeding), step-relations, and the four-wife limit.

The substantive issues addressed in this entry concern the implicit framework, not specific prohibited categories:

1. Marriage as comprehensively legislated. The Quran and hadith provide an extensive framework of marriage prohibitions. This is itself notable: religious law as comprehensive family-law code.

2. Child marriage normalised. The framework establishes prohibited marriage categories without prohibiting marriage by age. Pre-pubescent marriage (entries q05, b01, d06, t04, n05) is not in the prohibited categories. The framework's omission is itself permission. A further Quranic signal is Q 65:4, which specifies a waiting period after divorce for wives "who have not yet menstruated" — classical jurists across all four schools cited this verse as proof that prepubescent marriage was Quranically assumed. The classical Hanbali jurist Ibn Qudama (Al-Mughni, d. 620/1223) records that scholars had reached consensus on the father's ability to compel his prepubescent virgin daughter's marriage, citing the Aisha precedent as agreed-upon proof; Robert Spencer, The Truth About Muhammad (Regnery, 2006), argues that the Quran and hadith offer no record of any contemporary challenge to this practice, which is what distinguishes it from a mere cultural norm.

3. The radhāʿa framework. Foster-relations created by breastfeeding extend the prohibition. This includes the adult-breastfeeding case (entry m08) — establishing kinship through suckling that bars subsequent marriage. The framework permits unusual ritual constructions of kinship. Kecia Ali, Marriage and Slavery in Early Islam (Harvard University Press, 2010), demonstrates that the same legal vocabulary of ownership and control used for slavery also structured the jurisprudence of marriage kinship — the radhāʿa rules among them — in the Maliki, Hanafi, and Shafi'i schools.

4. The four-wife limit. Q 4:3 establishes a four-wife limit for ordinary Muslim men, with the requirement of equal treatment (Q 4:129). Muhammad himself was exempt (entry q16). The structural exemption for the prophet illustrates the framework's gender-asymmetric structure.

5. Wali requirement. The wali (male guardian) requirement (entry d15) intersects with the marriage framework. The combination produces a system where adult women cannot independently contract their own marriages. Kecia Ali, Marriage and Slavery in Early Islam (Harvard University Press, 2010), demonstrates that across all four classical Sunni legal schools guardianship (wilaya) is structurally indispensable to the marriage contract, with the legal rhetoric of control and ownership pervading the entire institution — fathers in the Maliki, Hanafi, and Shafi'i schools alike could contract the marriage of virgin minors with no consent required from the girl.

6. Modern application. The framework continues to operate in Muslim family law across the Muslim-majority world. Modern reform efforts have addressed specific issues (minimum marriage age, dowry rights, wali flexibility) but generally preserve the underlying structure. Lynn Welchman, Women and Muslim Family Laws in Arab States (Amsterdam University Press, 2007), documents that even where Arab states have codified or amended Muslim family law, the structural pillars — guardian requirement, polygyny permission, and asymmetric divorce — remain intact in virtually every jurisdiction surveyed. Jonathan A. C. Brown, Misquoting Muhammad (Oneworld, 2014), similarly notes that classical jurisprudence on marriage was constructed over centuries by the clerical class and resists straightforward abrogation even where modern Muslim reformers seek change.

7. Comparison with modern marriage law. Modern legal systems treat marriage as a contract between adult equal parties. The Islamic framework treats marriage as a religiously-regulated transaction with specific gender roles, age categories, and family-involvement requirements. The two frameworks differ in fundamental structure.