The Glorified Allah commands:
“Oh you who believe! Intoxicants, gambling, idols, arrows for seeking the future or luck are all abominations, the works of the strayed. So, keep away from them that you may attain the true success.” (Al-Ma’ida/ The Feast 5:90)
The word “khamr” in the verse describes especially alcoholic beverages and also all kinds of solid and liquid foods and beverages which unbalance mankind mentally and spiritually.
The Messenger of Allah (may peace be upon him) said that “All kinds of intoxicating items are unlawful.” (See: Muslim, Drinks, 73; Abu Dawood, Drinks, 5; Tirmidhi, Drinks, 1)
Using marijuana and all these kinds of drugs are unlawful because they intoxicate and narcotize human. We have to abstain from them. Such agents disrupt the nervous system and destroy the ability of thinking and willpower. The people who use these kinds of agents get disconnected from the outside world and lose their self-respect. They are easily ready to perpetrate a crime and all kinds of evil. Modern medicine, psychology and social sciences have a common opinion that the marijuana, opium, heroin, cocaine and other similar drugs or stimulant substances are more harmful than alcoholic beverages to human health and the social order.