She vowed to sacrifice a sheep on behalf of her mother; can she offer the charity in the form of money instead?
Question

                My mother was sick and she died two years ago. I had vowed that if Allaah granted me abundant provision by His grace, I would give charity by slaughtering a sheep in Ramadan of that year, and I would give the reward for that to my mother. I work in a school and I receive a monthly salary of 5000 riyals, but I give it to my husband who is in need and is the head of a large family with little income. He built a house for us and owes debts to a lot of people. Hence I am helping him with my monthly salary and that year I was not able to fulfil my vow, but I used to give 1000 riyals from my salary to my sister, so that she could give in charity to the poor and I donated the reward of this charity to my mother. Is this sufficient to fulfil the vow, or do I have to give charity by sacrificing a sheep as I specified, even if the year in which I stated that I would do that has gone?.
Praise be to Allah.
    Firstly: 

    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”

    [al-Insaan 76:7]

    “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”

    [al-Baqarah 2:270]

    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”

    [al-Maa’idah 5:89]

    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.