Dr Zakir Naik,As far as smoking is concerned several years before where science hadn't advanced that far, most of the scholars used to say that smoking is Makhrooh based on the Hadith of Muhammad (saws) which is mentioned in

Sahih Bukhari Vol. no. 1 in the Book of Adhan Hadith no. 855 where the Prophet said that

"Anyone who eats garlic or onion, they should stay away from us and stay away from the mosque"

Prophet said that, you know, that don't come to the mosque after having garlic or onion because it gives bad breath. When you are smoking the breath is worse then onion or garlic so based on this Hadith therefore garlic and onion doesn't become haraam, it becomes Makhrooh so based on this Hadith scholars give the Fatwa that smoking is Makhrooh

But now after science has advanced we have come to know that smoking is nothing but it's a slow poisoning. Tobacco in any form whether in smoking cigarettes whether bedi whether tobacco in Huqqa whether chewing tobacco all forms of tobacco contain nicotine and tar and we know its nothing but slow poisoning. That's the reason most of the non-Muslims also, they agree that smoking is Haraam. Not only the Muslim world even the non-Muslims. That's the reason they put a statutory warning on the cigarette packs, they put a statutory warning saying "Cigarette smoking is injurious to health" or in some countries it mentions "General Surgeon's Warning" or "Surgeon General's warning: Smoking is injurious to health".
And anyone gives an add whether in newspaper or in the magazine or television it is compulsory that they have to highlight this statement "Smoking is Injurious to Health" so I am not talking about the Muslim world even the non-Muslim world agrees that smoking is nothing but slow poisoning.