What is the required time for forming the intention for an obligatory fast?
General Chapter
Al-Mughni
Book of Fasting
Primary text
The intention for an obligatory fast, such as Ramadan, must be formed from the night before dawn. The evidence is the hadith from Hafsah: "Whoever does not form the intention to fast from the night, then he has no fast," and a similar narration from 'Aishah. Furthermore, since it is an obligatory fast, it requires the intention from the night, like making up a missed fast.
Supporting text
Some Shafi'i scholars stipulate that the intention must be formed during the latter half of the night. However, the comprehensive wording of the hadith, "whoever does not form the intention to fast from the night," allows for any time during the night. Specifying the latter half leads to the potential failure of the fast, as that time is generally associated with sleep. Moreover, the justification for permitting the call to prayer (Adhan) and departure from Muzdalifah after Fajr does not apply to the intention, as those acts remain permissible after dawn, whereas the intention for fasting becomes invalid if delayed past Fajr.