1. A person takes a vow that if a certain wish or work of his is fulfilled, he will undertake to carry out a certain act of ibaadah. Once this wish or work of his is fulfilled, it will be wajib upon him to carry out the act of ibaadah which he had vowed to carry out. If he does not fulfil this vow, he will be committing a great sin. However, if a person takes a useless vow which has no basis in the Shariah, it will not be wajib on him to fulfil such a vow. Vows of this sort will be mentioned later.
2. A person says: “O Allah! If a certain task is fulfilled, I will keep five fasts for Your pleasure.” Once this task of his is fulfilled, he will have to keep these five fasts. But if the task is not fulfilled, he will not have to keep these fasts. If the person merely said that he will keep five fasts, he has the choice of keeping them continuously one after the other, or of keeping them separately. But if he said that he will keep five fasts continuously or had this intention in his heart, he will have to keep them one after the other. If he misses out one or two fasts in between, he will have to start all over again.
3. If the person says that he will fast on Friday or that he will fast from the 1st till the 10th of Muharram, then it is not necessary for him to fast specifically on a Friday or specifically on those days of Muharram. He could keep these 10 fasts whenever he wishes irrespective of whether he keeps them in Muharram or in any other month. The only condition is that he should keep them continuously. Similarly, if he says: “If this work of mine is fulfilled today, I will fast tomorrow”, he has the choice of fasting whenever he wishes.
4. While taking a vow, a person said: “I will keep the fasts of the month of Muharram.” He will now have to keep fasting continuously in the entire month of Muharram. If he misses a few fasts in between, he will have to keep them after the month of Muharram. He does not have to keep all the fasts all over again. He also has the choice of fasting in any other month. It is not necessary for him to fast in Muharram. The only condition is that he has to keep these fasts continuously without missing any.
5. A person takes a vow that if he finds a certain item which he lost, he will offer eight rakaats of salaat. Upon finding his lost item, he will have to offer eight rakaats of salaat. He has the choice of making the intention of offering all eight rakaats at once, offering four rakaats at a time or offering two rakaats at a time. And if he took a vow of offering four rakaats, then he will have to offer all four with one salaam. If he offers two rakaats at a time, his vow will not be fulfilled.