All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all His family and companions.
A vow is an act of worship that Allah has enjoined fulfilling. He, The Almighty, said, "Then let them complete the rites prescribed for them, perform their vows, and (again) circumambulate the Ancient House."{Al-Hajj, 29}. Moreover, Allah has praised the ones who fulfill their vows where He, The Exalted, said, "(Because) they perform the vow and fear a day whereof the evil wide-spreading,"{Al-Insan, 7}.
It is incumbent upon every Muslim person to fulfill his vow as long as he is capable to; otherwise, he remains liable for it.
Al-Imam An-Nawawi said, "When a person makes his vow conditional upon the occurrence of a good thing to him or that a given bad thing doesn`t affect him, then he`s obliged to fulfill it."{al-Majmou`, 8/458}.
It is better that you fulfill exactly what you had intended, as is the view of the Shafie school of thought. In addition, Hanafiejurists permitted giving all types of Zakat, vows and expiations in the form of money, as stated in the book {Rad Al-Mohtar}, "If he vowed to give this gold dinar to charity, and gave its value in Dirhams, then that is permissible. Or, if he vowed to give bread to charity and gave its value in the form of money, then that is permissible according to our school of thought{Hanafie}.
In principle, you must fulfill exactly what you had intended in order to be on the safe side and clear yourself from liability. In addition, there is no harm in following the opinion of the Hanafie jurists so long as the given money is equal to the value of the vowed item. And Allah knows best.
