Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Volume 23, Page 6, Fatwa No.16827
Question: Regarding the expiation of an oath (kaffaaratul-yameen), could you please advise us about the manner in which the obligation of feeding the ten poor and destitute [must take]? Is it [required to feed them] for a whole day, or [just] a single meal for each [poor and destitute] person; And what is the cost [entailed]? And is it permissible to [simply] pay [the poor and destitute] the cost of feeding [them] in money or not?
Response: The expiation of an oath is to feed ten poor and destitute people, with each one receiving half a saa’ of wheat, dates, rice, or the like from the staple food of the land. And [note] half a saa’ amounts to one and a half kilos [in weight]. Or [alternatively], one can clothe ten poor and destitute people – with each receiving a shirt, or [instead] free a believing slave.
If he is unable to carry out any [one] of the aforementioned three [legislated options], then he is required to fast for three days, [bearing in mind] the [cash] payment [to the poor and destitute individuals] for the expiation of an oath will not be rewarded (accepted).
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu `alayhi wa sallam) and his family and his companions.