Praise be to Allaah.
The expiation for breaking
an oath (kafaarat yameen) is, as Allaah says, freeing a slave or feeding or
clothing ten poor persons. If that is not possible then it is fasting for
three days.
Allaah says (interpretation
of the meaning):
“Allaah will not punish
you for what is unintentional in your oaths, but He will punish you for your
deliberate oaths; for its expiation (a deliberate oath) feed ten Masaakeen
(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 Allaah makes clear to you His Ayaat (proofs, evidences, verses,
lessons, signs, revelations, etc.) that you may be grateful”
[al-Maa'idah 5:89]
Thus it is known that it is
not valid to offer expiation by fasting, except for one who cannot afford to
feed or clothe ten poor persons, or to free a slave.
See the answer to question
no. 45676 for details on expiation
for breaking an oath.
Secondly:
If your father is not able
to feed or clothe ten poor persons or to free a slave, but he is able to
fast, then he must fast, and it is not valid for you to fast on his behalf.
The one who has fasted all of Ramadan is not incapable of fasting for three
days, whether consecutively or separately.
If he is unable to fast,
then the expiation is waived in his case.
Shaykh Ibn ‘Uthaymeen (may
Allaah have mercy on him) said: If a person has to offer expiation for
breaking an oath and he cannot afford to feed (ten poor persons) and he is
not able to fast, then it is waived in his case because Allaah says
(interpretation of the meaning):
“So keep your duty to
Allaah and fear Him as much as you can”
[al-Taghaabun 64:16]
“Allaah burdens not a
person beyond his scope”
[al-Baqarah 2:286]
and the Prophet (peace
and blessings of Allaah be upon him) said: “If I order you to do a thing, do
as much of it as you can.” And he does not have to do anything else, because
one of the established principles of Islam is that duties are waived if a
person is unable to do them and he may do the alternative if an alternative
exists, or something else if there is no alternative. If he is unable to do
the alternative then it is waived altogether. End quote from Fataawa Noor
‘ala al-Darb.
Whatever the case, your
fasting on his behalf is not valid, because he is the one who has to offer
expiation for breaking his oath.
And Allaah knows best.