Is Smoking Allowed in Islam? why?

Islamic scholars have historically had mixed views about tobacco, and until recently, there has not been a clear, unanimous fatwa (legal opinion) to allow or forbid cigarette smoking.

However, there are many instances where the Qur'an gives us general guidelines, and calls upon us to use our reason and intelligence, and seek guidance from Allah about what is right and wrong. Islamic scholars use their knowledge and judgment to make new legal rulings (fatwa). In the Qur'an, Allah says, “...he [the Prophet] commands them what is just, and forbids them what is evil; he allows them as lawful what is good, and prohibits them from what is bad..." (Qur'an 7:157).

In more recent times, as the dangers of tobacco use have come to be proven beyond any doubt, scholars have become more unanimous in pronouncing tobacco use clearly haram (forbidden) to believers. They now use the strongest terms to condemn this habit. Here is a clear example:

"In view of the harm caused by
tobacco, growing, trading in and
smoking of tobacco are judged to
be haram (forbidden). The Prophet, peace be upon him, is reported to have said, 'Do not harm yourselves or others.'
Furthermore, tobacco is unwholesome, and God says in the Qur'an that the Prophet, peace be upon him, 'enjoins upon them that which is good and pure, and forbids them that which is unwholesome'"

[[REFRENCE :(Permanent
Committee of Academic Research
and Fatwa, Saudi Arabia)]]