what is the Kaffarah (expiation) for an oath?
Kaffarah (expiation) for an oath has been clarified in the Ayah (Qur'anic verse) which reads:
Allâh will not punish you for what is unintentional in your oaths, but He will punish you for your deliberate oaths; for its expiation feed ten Masâkîn (poor persons), on a scale of the average of that with which you feed your own families, or clothe them or manumit a slave. But whosoever cannot afford (that), then he should fast for three days. That is the expiation for the oaths when you have sworn. And protect your oaths (i.e. do not swear much). Thus Allâh make clear to you His Ayât (proofs, evidence, verses, lessons, signs, revelations, etc.) that you may be grateful.
Feeding means to give every Miskin (needy) half a Sa` (1 Sa`=3 kg. Approx.) from the staple food of the country, such as dates and the like. Another option is to serve a lunch or a main meal for every Miskin from the average meal that you feed your family. Clothing the Miskins involves giving each of them a garment that would be sufficient to perform Salah (Prayer) while wearing it. For example, you may give every Miskin a garment or an Izar (garment worn below the waist) and a Rida' (garment worn around the upper part of the body) if they are accustomed to wearing that kind of clothes. (Part No. 23; Page No. 6) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.