How is fasting in fulfillment of a vow (nadhr) observed?

A nadhr or vow means that a person makes it obligatory to himself by making a promise to Allah that he will perform a fard or wajib type of worship that is not fard or wajib upon him. Absolute vows without a certain condition and time needs to be fulfilled as soon as possible after the moment of making the vow. Conditional vows need to be fulfilled when the condition is realized. Fulfilling the requirement of the vow before the condition happens is invalid, and the person needs to fulfill it again after the condition is realized. Nadhr fasting with a certain time needs to be performed on its due time. While making intention for such fasting, one is not required to state clearly that it is a fasting of nadhr. Nadhr fastings without a specified time may be performed anytime except Ramadan and the days when fasting is prohibited. But this fasting needs to be performed with the intention of nadhr. In this regard, nadhr fasting is performed the same way it is promised. For example, if it is promised to be observed consecutively, then the person should perform it consecutively without break. If not, one can observe it by giving breaks. But it is not performed on the days when fasting is not permissible (Ibn Abidin, Radd al-Muhtar, III, 334, 422, 424).

Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS,

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