Answered by Shaykh Amjad Rasheed
Translated by Ustadha Shazia Ahmad
Since it is unlawful to consume harmful things, such as smoking cigarettes, then how is it permissible to consume sugar and tea, when we know that they can be harmful?
The criterion according to our scholars about which pure substances are permissible to consume and which are not is that if something is will cause harm more than 50% of the time, it is unlawful to consume. If something only causes harm rarely, or if it causes harm half of the time and does not cause harm the other half of the time, then it is not unlawful to consume, but it is disliked, as the erudite scholar Ibn Hajar said in his commentary on the Tuhfa. See Shirwani: 1/75.
Based on the above, we say that it is unlawful to smoke tobacco because it is clear than it harms people most of the time and that it is rare for a smoker to remain unharmed by it. This is in contrast to sugar and tea, whose consumption does not harm people most of the time; rather, the harm is rare.
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One should note, however, that if a doctor informs a certain person that a certain thing would harm him specifically if he consumed it because of a condition that he suffers from, then it would be unlawful for that person to consume it even if it is something that normally harms people only rarely, as stated by Ibn Hajar in his discussion on using water heated by the sun. The same would apply if a person knowns through his own experience that consuming something would harm him [i.e., it would be unlawful for him to consume that thing].
وعليه فيُقال: يحرم تناول الدخانِ المعروفِ اليومَ فإنه لا يخفى أن ترتب ضرره عليه هو الغالب وأن السلامةَ من ضرره هي النادرة، بخلاف نحو السُّكَّر والشاي فالغالبُ فيهما عدم ترتب الضرر بل ذلك فيها نادر، وقد صرَّح أئمتُنا بأن استعمال الماء المشمس يترتب عليه الضرر أي وهو حصول البرص، ومع ذلك حكموا بكراهته فقط لأجل أن ترتبَ ذلك نادر لا غالب، نعم إن أخبر طبيبٌ بأن الشيءَ الفلاني يضرُّ شخصاً بعينه لمقتضٍ قام بمزاجه حرم على ذلك الشخص تناوله وإن كان في الأصل يندر ترتب ضرره عليه كما صرَّح به ابن حجر في الكلام على
المشمس، ومثلُ إخبار الطبيب معرفةُ الشخص نفسه بذلك.