I vowed to prepare a dinner on my own, covering all the costs, but my sister said she would share the cost of the meal with me. What is the ruling?

Question:
I said: I made a vow that if my mother recovered, I would prepare a dinner and do it alone, covering all the costs. My mother recovered, praise be to Allah, and she came out of the operation successfully. My sister said she would share the cost of the meal with me because she got a job. What is the ruling?

Answer:
The ruling is that it is not... it is obligatory for you. It is obligatory for you to fulfill the vow. So if someone helps you in carrying it out, there is no harm. If someone helps you in carrying it out, it is as if you are coming from my personal money and no one is helping me, so do not accept the help. But if you did not stipulate this, and you only vowed to prepare food when your mother recovered, and may Allah heal her, and someone came to help you or took the burden off you and did it, there is no harm.