Why Is Smoking Haram?
Question

Why is smoking haram?
Praise be to Allah.The reasons why smoking is haram
1.Islam forbids everything that is harmful
Perhaps you know that all nations of the world – Muslim and kafir alike – have now started to fight smoking, because they know that it is very harmful. 
Islam forbids everything that is harmful, because the Prophet (peace and blessings of Allah be upon him) said: “There should be no harming or reciprocating harm.”  
Undoubtedly there are foods and drinks which are beneficial and good, and others which are harmful and bad. Allah described our Prophet (peace and blessings of Allah be upon him) in the following terms (interpretation of the meaning):
“…he allows them as lawful At Tayyibat (i.e. all good and lawful as regards things, deeds, beliefs, persons and foods), and prohibits them as unlawful Al Khabaith (i.e. all evil and unlawful as regards things, deeds, beliefs, persons and foods)” [al-A'raf 7:157]
Is smoking one of the good and lawful things (al-tayyibat) or one of the evil and unlawful things (al-khabaith)?
2.Spending on smoking is spending on something harmful 
It was narrated that the Prophet (peace and blessings of Allah be upon him) said: “Allah forbids you to trade gossip, to ask too many questions and to waste money.” And Allah forbade wasteful extravagance when He said (interpretation of the meaning):
“and eat and drink but waste not by extravagance, certainly He (Allah) likes not Al-Musrifun (those who waste by extravagance)” [al-A'raf 7:31] 
And He described the slaves of the Most Merciful as follows (interpretation of the meaning):
“And those who, when they spend, are neither extravagant nor stingy, but hold a medium (way) between those (extremes)” [al-Furqan 25:67]
The whole world now knows that the money spent on smoking is to be considered as money wasted, from which no benefit is gained. Indeed, it is money spent on something harmful. 
If the money which is spent on smoking worldwide were to be collected, it could have saved entire populations who have died of starvation. Is there anyone more foolish than one who holds a dollar bill and sets fire to it? What is the difference between him and the one who smokes? Indeed, the smoker is more foolish, because the folly of the one who burns a dollar bill ends there, whilst the one who smokes burns his money and also harms his body.
3.Smoking has caused many disasters
How many disasters have been caused by smoking, because of cigarette butts which are thrown away and cause fires. Other disasters have been caused in other ways, as when a house was burned down with its occupants inside, when a man lit his cigarette when there was a gas leak.
4.Many people are offended by the smell of smokers
How many people are offended by the smell of smokers , especially when you are unfortunate enough to have one of them standing next to you in the mosque. Probably any nasty smell is easier to bear than the smell of the smoker’s mouth when he has just woken up. It is amazing how many women can put up with the smell of their husbands’ mouths! 
The Prophet (peace and blessings of Allah be upon him) forbade those who had eaten garlic or onions from coming to the mosque so that they would not offend their fellow-worshippers with their smell. The smell of onions and garlic is easier to bear than the smell of the smoker and his mouth. 
These are some of the reasons why smoking is haram. 
 And Allah knows best.