In Shia Islam, smoking is considered haram (forbidden) if it is believed to cause significant harm to one's health.
Islamic teachings emphasize the preservation of health and life. Self-harm is strictly prohibited. Therefore, if an individual believes, based on credible evidence or personal experience, that smoking poses a substantial risk to their well-being, then it is considered haram for them. The key factor is the potential for harm. If smoking is not perceived to cause considerable harm, then the ruling might be different, although still discouraged due to its detrimental effects.
Ultimately, it is up to each individual, based on their understanding of the potential health risks and their own religious beliefs, to determine whether smoking is permissible for them. Consulting with a knowledgeable religious scholar (Marja') is also recommended for a more personalized ruling.
