For kafaarat yameen it is not sufficient to feed one poor person ten times
Question

                Is it permissible for me to give kafaarat yameen to one poor person, i.e., by feeding him ten times, or must it be given to ten poor persons?.
Praise be to Allah.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)”

    [al-Maa’idah 5:89]

    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.”.