Question: He wants to know whether fasting five days is enough simply for going back to smoking, or whether—as he stipulated—he must fast five days for every single cigarette.

Answer: No. This vow takes the same ruling as an oath, because his aim was to keep himself from that act. According to the opinion preferred by Shaykh al-Islam Ibn Taymiyyah, it is treated like an oath, and its expiation has already been paid. He himself said, “Whenever I smoke I will fast five days.” That means the vow is still in force and has not been dissolved, so every time he smokes a cigarette he must fast five days. The vow therefore remains binding. He is obliged to quit smoking even without a vow; how much more so after having made one. Should he smoke, he must fast five days—each and every time—for he said, “Whenever I smoke, for every cigarette.” Thus we tell him, “Fast five days.” In other words, the vow is renewed every time he lights a cigarette, which is yet another reason for him to abandon this vile habit altogether.

Accordingly, he must fast five days for every cigarette, exactly as he vowed.
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Question: I vowed to fast a month for the sake of Allah, but I did not specify which month. Can I fulfil the vow by fasting thirty separate days, or not?

Answer: Whoever vows to fast a month without specifying which one, the jurists say he has two choices. He may either fast an actual lunar month—if so, the fasts must be consecutive—and that suffices even if the month is twenty-nine days, because that still counts as a month.