Answered by Shaykh Amjad Rasheed
What is the Islamic ruling on smoking?

No two people, not even smokers, differ that smoking is a foul act that human nature finds revolting because of its awful smell on the one hand, and on the other hand because of the harm—established with certainty by medical experts—that it brings to the smoker himself and those who keep his company. Because of this, smoking is forbidden and it is not permitted to engage in it or sell [h: tobacco] because of His Most High’s saying in description of His honorable prophet, “He permits them pure things and forbids them the foul,” [m: (7:157)] His Most High’s saying, “Do not cast yourselves into destruction,” [m: (2:195)] and because of [m: the Prophet’s] (Allah bless him and grant him peace) saying, “There is to be no harm nor reciprocating harm.” [m: (Ibn Majah, Al-Daraqutni, Al-Muwatta’)] The prohibition is stronger if one buys [m: tobacco] with [m: money] one needs to support one’s dependents, as happens with some foolish people.
As for what some people repeat, that smoking is disliked and not forbidden, it is because the Devil has embellished [m: this act] for them even though they are certain of its harm, as is witnessed among many smokers. As for scholars who long ago said it was disliked, this is because its harm had not yet been decisively established, as it has today. Even then, some of those who said it was disliked, such as Imam Bajuri, Sheikh of Al-Azhar and imam of the Shafi‘is of his age, explicitly stated that it is prohibited if its harm is established with certainty. (Hashiya Al-Bajuri ‘Ala Ibn Qasim, 1.357.)
Amjad Rasheed
Amman, Jordan
(Translated by Moustafa Elqabbany and Hamza Karamali)