Answered by Shaykh Abdul-Rahim Reasat
Question: Assalamu alaykum
I made an oath that if commit a certain sin then I will fast 40 days. Due to temptation I have committed that very sin. Do I have to fast for 40 days?
Answer: As-salamu ‘alaykum wa rahmatullah wa barakatuh
I pray you are well.
You may fast the 40 days, or perform the expiation of an oath; the choice is yours. Normally, if someone swears the he will perform a particular act of worship if a particular situation takes place (nadhr), he must do so if he the condition occurs. However, in your situation, your intention was to avoid a particular sin so this is also considered an oath from one perspective. Therefore, you may perform the expiation of an oath to absolve yourself should you choose to do so (Ibn Abidin, Radd al-Muhtar).
You have two options:
1. Fast for 40 days.
2. Perform the expiation of an oath, which is either:
a. Feeding 10 poor people
b. Clothing ten poor people.
If you cannot feed or clothe them, then fasting for three consecutive days will cover it.
Feeding the ten poor people is with two satiating meals on one day, or feeding one poor person for ten days. An alternative is to give them / him the monetary equivalent of the food instead. The amount payable is the value of 2.6 kgs or wheat flour, or 5.2 kgs of dates (al-Lubab, ed. Bashar Barkri ʿArabi). This amount was roughly the same in the past, but with wheat flour being much cheaper in our times it would be superior to give value of the dates, although the former is valid nonetheless.
Clothing them is with a normal set of clothes of medium quality or it’s monetary value.
May Allah grant you the best of both worlds.
[Shaykh] Abdul-Rahim Reasat