وَلَيْسَ عَلَى صَبِيٍّ وَلَا مَجْنُونٍ وَلَا مُكَاتَبٍ زَكَاةٌ.
Translation: There is no zakat due from a minor, an insane person, or a mukatab.
In the Hanafi position, a minor and a legally insane person are not addressed as liable in the same way as a legally competent adult. A mukatab is an enslaved person under a contractual emancipation agreement; his ownership is not treated as fully independent.
The three exclusions have different legal explanations: legal capacity in the first two cases, and completeness of ownership for the mukatab.