Praise be to Allah.
We should point out that the Muslim should not make vows, because the Prophet (blessings and peace of Allaah be upon him) said: “Vows do not bring anything forward or put it back, but vows are a means of getting something out of the miser.”
The Muslim should do good, give charity and draw close to Allaah, may He be glorified and exalted, in whatever ways Allaah makes easy for him, without making vows. But if he commits himself to do something, then he must fulfil it, if his vow is a vow to do an act of obedience. The Prophet (blessings and peace of Allaah be upon him) said: “Whoever vows to do an act of obedience to Allaah, let him obey Him.” and Allaah says (interpretation of the meaning):
“They (are those who) fulfil (their) vows, and they fear a Day whose evil will be wide‑spreading”
“And whatever you spend for spendings (e.g., in Sadaqah — charity for Allaah’s Cause) or whatever vow you make, be sure Allaah knows it all”
So if a person makes a vow to do an act of obedience, it is obligatory for him to fulfil it. The questioner states that she vowed to sacrifice a sheep in a specific year and distribute its meat to the poor, and this is a vow to do an act of obedience, because sacrificing a sheep is an action done to draw close to Allaah, may He be glorified and exalted, and giving its meat in charity is a similar act of worship. She specified a particular time for that, so she should have fulfilled it at that time. As she delayed it and didn't do it at the proper time, she has to make up for it later on: she has to sacrifice what she vowed to sacrifice as an act of worship to Allaah, may He be glorified and exalted, and give its meat in charity, and this will be making up that action. And because of delaying, she has to offer kafaarat yameen (expiation for breaking a vow).
So she has to do two things:
1.Fulfil the vow that she made, making it up (qada’)
2.Offer expiation for breaking a vow due to the delay in fulfilling it.
The expiation for breaking the vow is as Allaah says (interpretation of the meaning):
“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”
That is kafaarat yameen.
As for her giving charity and giving money to her sister to give in charity, this is not acceptable as fulfilment of the vow, because the vow specified the sacrifice of a sheep and it did not mention charity in general terms. So that is not acceptable as fulfilment of the vow. There is reward for the charity that she mentions, and there is good in it, if Allaah wills, and we hope that the reward for it will reach her deceased mother, but it is not acceptable as fulfilment of the vow. And Allaah knows best. End quote.