As-salamu alaykum,
While smoking is detestable, I am afraid that at 17 your son is almost considered a young man now and in a few more years will be grown. Unfortunately at this age, the more you say “no”, the harder they push to do it. I would kindly suggest that when things are calm, take him out somewhere nice such as to lunch, a walk to the park, fishing, whatever he enjoys. Causally ask him what he plans for his future.

When he responds you can point out that it may be hard with emphysema or cancer or any other of the numerous health problems smoking brings. I would have some literature on some of the conditions with pictures and explanations. I would also tell him that if he wishes to quit, that you will be there to help him. While good health is a reward for quitting, often times a parent will help their child quit by setting up milestone rewards of their choosing as an incentive.

I do not know how long your son has been smoking, but he is probably addicted. In this case, if he agrees, you may want to get medical intervention such as the patch or gum to ease withdrawal symptoms. If he does not agree to quit, you can only continue to encourage good healthy habits, gentle reminders of the health consequences as well as the Islamic rulings on not destroying our bodies. By aligning yourself as a support system for him, you may get much further than with punitive measures.

We wish you the best brother, you are in our prayers.