The validity of fasting if the specific obligation is not intended, such as intending a supererogatory fast (nawafil) during Ramadan.
General Chapter
Al-Mughni
Book of Fasting
Primary text
According to one opinion held by some companions of Ahmad, if a person intends a supererogatory fast during the last day of Ramadan and it coincides with Ramadan, it suffices for the obligatory Ramadan fast. This view is also attributed to Abu Hanifa when the person is a resident. The rationale is that since the obligation (Ramadan) is established in a specific time, specifying the intention for it is not required, similar to the Tawaf al-Ziyarah (departure circumambulation).
Supporting text
Abu Hafs Al-'Ukbari stated that if one intends a supererogatory fast, it does not suffice for Ramadan; it must be intended from the night without doubt or ambiguity. The opposing argument asserts that since the fast is an obligatory act, specifying the intention is necessary, just as it is for makeup fasts. The analogy with Tawaf al-Ziyarah is rejected because if one performs Tawaf intending only Tawaf al-Wada' (farewell circumambulation) or general circumambulation, it does not suffice for Tawaf al-Ziyarah. Furthermore, Hajj is contrasted with fasting because Hajj can be initiated generally, whereas fasting requires specification.