وَأَكْثَرُهُ عَشَرَةُ أَيَّامٍ، وَمَا زَادَ عَلَى ذَلِكَ فَهُوَ اسْتِحَاضَةٌ.
Meaning: The maximum period of hayd is ten days; bleeding in excess of that limit is istihadah.
In Hanafi law, ten days is the maximum. Once bleeding exceeds this limit, the excess is not automatically menstrual; established habit and istihadah principles are relevant to classification.
This maximum operates as a basic rule before examining individual patterns of bleeding.