It is universally accepted that smoking has many serious health and life hazards among which is lung cancer. These hazards affect not only the smoker, but those around him or her as well. Shari`ah has stressed the importance of being in good health to the extent that Prophet Muhammad (peace and blessings be upon him) even advised Muslims in all ages to strike a balance between eating and drinking, so as to evade any harmful effects on the health.  

Smoking did not exist in the time of the Prophet (peace and blessings be upon him), but our great religion of Islam has laid down general principles from which many laws have been derived. In the Qur’an, Almighty Allah says, (Be not cast by your own hands to ruin, and do good. Lo! Allah loves the beneficent) (Al-Baqarah 2:195). Smoking causes fatal sicknesses, such as lung cancer, tuberculosis, etc.

In another verse, Almighty Allah says, (And do not kill yourselves) (An-Nisaa‘ 4:29). The Prophet (peace and blessings be upon him) is reported to have said, Whoever drinks poison, thereby killing himself, wil
l sip this poison forever in Hellfire.”

Given the above, scholars declare smoking as prohibited in Islam.

With regard to the question, the Standing Committee for Islamic Research and Ifta’ stated,

A muslim does not have to repeat the wudu’ after smoking, but he should remove the offensive odor from the mouth with something that can take it away. It is also obligatory to hasten to repent to Allah from that sin.