Answered by Shaykh Faraz A. Khan
Question: My question, specifically, is if you yourself placed terms within your oath to Allah, such as “If I commit such-and-such sin, I will fast 5 consecutive days”, and you happen to break this oath, will you only have to fulfill these terms? Or will you also have to pay kaffarah on top of it?
Answer: Assalamu alaikum wa rahmatullah,
I pray this finds you in the best of health and states.
Such a statement is a religious vow (nadhr), yet its form is a conditional statement that one does not want to occur (namely, committing the sin).
The ruling for such a statement is that if one does commit the sin, then one must either:
(a) fulfill the vow by fasting 5 consecutive days, or instead
(b) perform the general expiation of breaking an oath (yamin), which is to feed ten poor persons (2 meals each), or to clothe them (1 garment each), or to give them the equivalent monetary value. If one is unable to do that, one must fast three consecutive days.
So one has the choice of either (a) or (b).
[Ala’uddin Ibn Abidin, Hadiyaa Ala’iyya]
And Allah knows best.
Checked & Approved by Faraz Rabbani