Fulfillment of a vow in installments
11-8-2015 | IslamWeb
Question:
What is the sharia ruling on delaying the fulfillment of a vow when one is unable to do so immediately? If one vowed to give a specific sum of money, is it permissible to pay it in installments?
Answer:
All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If a vow has a specific time limit, then the vow maker has to give what he can offer of money when the fulfillment becomes due. He is also required to offer the expiation of an oath because of his inability to give the vowed sum in full. Ar-Ruhaybani 
a Hanbali scholar, said: "If one vowed to perform a specific amount of pilgrimages (Hajj) and then was able to perform only some of them, he should perform as many as he can and offer an expiation for being unable to perform the others."
If the vow is not time-limited and he intended to give the whole sum at once, then he should wait until he collects the sum in full and then give it. If he intended to give the sum in portions, then he should give what he already has and he remains liable for the rest of the sum until he obtains the money and gives it. Discussing the status of a person who vowed to slaughter a camel but is unable to do so or to slaughter its substitute of sheep in Hashiyat Ad-Dusooqi, the author said:
"If he is able to slaughter less than seven sheep, then he is not required to give any of this, according to the apparent meaning of the words of Ad-Dardeer and Al-Mawwaq. Rather, he should wait until he obtains the exact item specified in the vow (a camel) or its substitute (a cow) or its substitute (seven sheep). According to others, he is required to give what he can afford and then give the other portion whenever he can. It is the preponderant opinion because one is not required to give it all at once."
Allaah Knows best.