وَالزَّكَاةُ عِنْدَ أَبِي حَنِيفَةَ وَأَبِي يُوسُفَ فِي النِّصَابِ دُونَ الْعَفْوِ، وَقَالَ مُحَمَّدٌ وَزُفَرُ: تَجِبُ فِيهَا.
Translation: According to Abu Hanifah and Abu Yusuf, zakat attaches to the nisab rather than the excess; Muhammad and Zufar say it attaches to the excess as well.
Nisab is the threshold on which a specified zakat due is charged. ‘Afw is the additional livestock between successive thresholds that does not yet trigger another complete prescribed amount.
For instance, forty sheep attract one sheep, and eighty still attract one sheep. The additional animals between the thresholds are the “excess” discussed here; jurists differ on whether they share in the legal basis of the liability.