—whether that incapacity pertains to ability or to choice.

Accordingly, if a person eats, drinks, or commits any other act that would normally break the fast during the daytime in Ramadan—or while observing any other fast—he should nevertheless complete his fast; it remains valid, for the act was not voluntary on his part. Rather, it was Allah who fed him and gave him drink.

Scholarly disagreement
The majority of jurists maintain that eating or drinking done forgetfully does not invalidate the fast. Their point of contention lies with sexual intercourse: does it, like eating and drinking, leave the fast intact when done out of forgetfulness, or not?

Imam Ahmad and the Hanbalis hold that intercourse invalidates the fast even when the person was ignorant or forgetful. Should it occur during the daylight hours of Ramadan it also obligates an expiatory penalty, a stance unique to the Hanbali school. Their evidence is the hadith’s wording, which limits the ruling to eating and drinking, thereby implying that intercourse is treated differently. They also argue that genuine forgetfulness with respect to intercourse is improbable, unlike eating and drinking.

In contrast, the imams Abu Hanifah, al-Shafi‘i, Dawud, Ibn Taymiyyah, and others contend that such intercourse does not break the fast. They cite three lines of proof:

1. Al-Hakim narrates from Abu Hurayrah (may Allah be pleased with him): “Whoever breaks his fast in Ramadan out of forgetfulness is not required to make it up, nor to offer expiation.” Ibn Ḥajar graded the report authentic, and the phrase “breaks his fast” is general, covering intercourse as well as other acts.
2. The inclusive texts, such as the Almighty’s words: “Our Lord, do not take us to task if we forget or make a mistake” (Q 2:286), and the hadith: “My community has been pardoned for errors, forgetfulness, and what they are compelled to do.”
3. Even those who deem the fast invalid in this case agree that no sin is incurred. Once excuse is acknowledged, it should apply comprehensively; there is no basis for drawing distinctions.

They answer the Hanbali argument by saying that limiting the ruling to eating and drinking is merely an instance of attaching a legal judgment to a specific example, which does not preclude the same ruling from applying to other cases.

Lessons derived from the hadith

1. The fast remains valid for one who, out of forgetfulness, eats, drinks, or engages in intercourse.