The source divides fasting into obligatory and voluntary. It then divides obligatory fasts into assigned-time duties and duties outstanding in one’s liability. The first group includes Ramadan and a specified vow; the second includes Ramadan make-ups, unspecified vows, and expiations.
The first group and nafl permit a qualified daytime intention; the second requires a specified intention the previous night. Later Hanafi works narrow the practical timing to before the legal-day midpoint. The next lesson examines the Ramadan crescent.