What is the ruling on one who swore by Allah and covenanted with Allah to quit smoking, then returned to it after four years, and what are the implications of his statement: "And if I return [to it], then upon me be the curse of Allah and His angels and all mankind, and [may I be] in Hell, abiding eternally therein with Abu Jahl and Abu Lahab and Ubayy ibn Khalaf"?

Smoking is forbidden due to the harms that result from it. The sin increases if the smoker swore to quit it, made a covenant with Allah, and promised his father to do so, and then broke his oath. The smoker must repent, seek forgiveness, and quit smoking. He is required to offer a single expiation for breaking an oath. He is not obliged to do anything regarding the exaggerations in his oath, such as cursing or anything else; rather, he should seek forgiveness from Allah.