What is required of a smoker who vowed to quit cigarettes, and returning to them necessitates fasting one day or reciting five parts of the Qur’an for each cigarette, and he has since returned to them and smoked the equivalent of 27 khatmas? And what is required of him in the future?

The person who made the vow (nadir) must repent to Allah, for smoking is Islamically forbidden. If it is established that smoking is forbidden and abstaining from it is obligatory, then according to the majority of scholars, a vow to do an obligatory act does not constitute a valid vow, and the person is only required to repent. For those who consider it valid, the vow falls under the category of a "vow of obstinacy" (nadhr al-lajaj), and the person who made the vow has the choice between fulfilling the vow (fasting for a day or reciting five parts of the Quran) or offering an expiation for a broken oath (kaffarat yamin).