It is not sufficient to offer kafaarat yameen by feeding one poor person numerous times.
With regard to kafaarat yameen – and other kinds of kafaarah (expiation) – it is essential to look for the number of poor persons mentioned in the texts.
Ibn Qudaamah (may Allaah have mercy on him) said in al-Mughni:
If a person who owes an expiation can find the right number of poor persons, it is not sufficient for him to feed less than ten in the case of kafaarat yameen, or less than sixty in the case of expiation for zihaar (a jaahili form of divorce) or for having intercourse (during the day) in Ramadaan. This is the view of al-Shaafa’i, because Allaah says (interpretation of the meaning):
“for its expiation (a deliberate oath) feed ten Masaakeen (poor persons)”
Whoever feeds one person, then he has not fed ten, therefore he has not obeyed the command and that is not sufficient. End quote.
It says in Fataawa al-Lajnah al-Daa’imah li’l-Ifta (23/21):
If kafaarat yameen (expiation for breaking a vow) is offered in the form of food, it is essential to give it to ten poor persons, giving each one half a saa’ of food. It is not sufficient to limit it to one poor person, even if you repeat that for ten days, because this is contrary to the text.”.