Which discipline directly addresses “How many days of fasting does this particular expiation require?”

The Four Proofs: Fiqh, Uṣūl al-Fiqh and Kalām

• Uṣūl: the general conditions of legal proofs
• Fiqh: a particular practical ruling
• Kalām: detailed proof of doctrines
• Only the history of fatwā, not substantive fiqh