In the Name of Allaah, the Most Gracious, the Ever Merciful…
MARIJUANA as a medical treatment?! REALLY?
Muslims, let us please go back to our scholars on such issues!
“Seeking medical cures from filthy (haraam) substances is proof of a sickness in the heart…”
What follows is a complete translation of a detailed answer given by Shaykh al-Islaam Ibn Taymiyyah [d.728] (may Allaah have Mercy on him) when he was asked about a patient whose doctors told him that the only (effective) medical treatment in his situation would be to consume intoxicants, canine (dog) meat, or even swine. He replied:
It is not permissible to use intoxicants and other filthy substances as medical treatments, based on what was reported by Waa’il ibn Hujr,  who said that Taariq ibn Suwayd al-Ju’fee  asked the Prophet (may Allaah raise his rank and grant him peace) about intoxicants, and he forbade him from using them. Taariq added, “But I only use them as medical treatments.” He (the Prophet) responded:
إنه ليس بدواء ولكنه داء
“It is not a treatment, however it is a disease (itself).”
This (hadeeth) was collected by Imaams Ahmad and Muslim in his Saheeh. 
And on the authority of Aboo ad-Dardaa’, the Messenger of Allaah (may Allaah raise his rank and grant him peace) said:
إن الله أنزل الدواء وأنزل الداء وجعل لكل داء دواء، فتداووا ولا تتداووا بحرام
“Verily Allaah has sent down illnesses, and He has sent down the cures. He has made (available) a cure for every illness, so take medical treatments, but do not treat illnesses with haraam (substances).”
This (hadeeth) was collected by Aboo Daawood. 
And Aboo Hurayrah said, “The Messenger of Allaah (may Allaah raise his rank and grant him peace) forbade the use of filthy substances as medical treatments.” In one narration (of this report), “He meant: poison.” It was collected by Ahmad, Ibn Maajah, and at-Tirmithee. 
And on the authority of ‘Abdur-Rahmaan ibn ‘Uthmaan : Once a doctor mentioned a certain medical treatment in the presence of the Messenger of Allaah (may Allaah raise his rank and grant him peace), and he mentioned that a frog was used as part of it. The Prophet (may Allaah raise his rank and grant him peace) then forbade the killing of frogs. It was collected by Ahmad, Aboo Daawood, and An-Nasaa’ee. 
‘Abdullaah ibn Mas’ood said about intoxication, “For sure, Allaah has not made your cure to be found in anything that He has forbidden you from.” Al-Bukhaaree quoted this in his Saheeh.  This was also reported by Aboo Haatim Ibn Hibbaan in his Saheeh as a statement of the Prophet (may Allaah raise his rank and grant him peace). 
These texts and other similar ones are explicit in their prohibitive wordings against using filthy substances as medical treatments. They explicitly declare using intoxicants as a medical treatment to be impermissible. Intoxicants are the mother of all filthy things, and they combine all types of sins (in the person who uses them).
Khamr (intoxicants) is a word used for everything that intoxicates, as is authentically established in texts from the Prophet (may Allaah raise his rank and grant him peace), as recorded by Muslim in his Saheeh, on the authority of Ibn ‘Umar, who said that the Prophet (may Allaah raise his rank and grant him peace) said:
كل مسكر خمر وكل خمر حرام [وفي رواية]: كل مسكر حرام
“Everything that intoxicates is khamr, and every kind of khamr is haraam.” [And in one narration,] “Everything that intoxicates is haraam.” 
In the two Saheehs [of al-Bukhaaree and Muslim] is the report of Aboo Moosaa al-Ash’aree, that he said: “O Messenger of Allaah! Give us your verdict on two drinks that we make in Yemen: al-Bit’a, made from thickeners added to honey, and al-Mizr made of thickened barley.” The Messenger of Allaah (may Allaah raise his rank and grant him peace), who was given the ability to speak with a few words that carry such heavy meanings, said:
كل مسكر حرام
“Every intoxicant is haraam.” 
Similarly is the report of ‘Aa’ishah that was collected in the two Saheehs [of al-Bukhaaree and Muslim] wherein she asked the Messenger of Allaah (may Allaah raise his rank and grant him peace) about al-Bit’a, a mixed honey drink drunk by the people of Yemen. He said:
كل شراب أسكر فهو حرام
“Every drink that intoxicates is haraam.” 
Also, Muslim, in his Saheeh, and an-Nasaa’ee and others collected a report from Jaabir, stating that a man from Habshaan in Yemen asked the Messenger of Allaah (may Allaah raise his rank and grant him peace) a drink used to make from corn flour (or cornmeal) called al-Mizr. He asked, “Does it intoxicate?” The man said, “Yes.” He replied:
كل مسكر حرام، إن على الله عهدا لمن شرب المسكر أن يسقيه من طينة الخبال
“Every intoxicant is haraam. Verily Allaah has a pact with every drinker of intoxicating beverages that He shall make him drink from the pus of wounds (of the people in the Hellfire)” 
All these narrations are explicit in declaring every type of intoxicant to be haraam, that they are all conisdered khamr, no matter what type it is, and that it is not permissible to use any of them as medical treatments.
As for what some doctors say, that the only cure for this disease is this specific medication, then this is merely the saying of an ignoramus. No one who really knows medicine would ever say that in the first place, let alone someone who (also) knows about Allaah and His Messenger. That is because cures are not restricted to one specific thing ordinarily, unlike how eating (food) directly leads to one’s hunger subsiding. There are some people whom Allaah heals without any medicine. Others are cured by Allaah after taking certain germ-based treatments, some halaal and some haraam. These same treatments could be used by other people who find no benefit, due to a missing (unknown, hidden) catalyst, or due to the presence of an (unknown, hidden) inhibitor. This is unlike how normal eating leads to the satisfaction of one’s appetite. Thus, Allaah has allowed starving people to eat filthy (impermissible) substances in times of need to satisfy their hunger, as it (food), and nothing else, removes the condition of (near-death) hunger. Without it, a person can die or become very sick. So when a way is known to solve such a problem, Allaah has made it permissible in that case, as opposed to medical treatments using filthy substances.
It has been said: Seeking medical cures from filthy (haraam) substances is proof of a sickness in the heart, and that is related to one’s faith. If he were from the believing nation of Muhammad, (he would know that) Allaah has not made his cure in something He forbade him from. Thus, if he were in dire need of food, he would be required to eat some dead (improperly slaughtered, normally impermissible) meat. However, medical treatments with permissible substances are not even obligatory in the first place (when known to be useful) according to most of the scholars. They even differed over whether it is better to take them (halaal medical treatments) or avoid them relying solely on tawakkul (trusting in Allaah)!
Something that clarifies this further is that when Allaah forbade dead (improperly slaughtered) meat, blood, pork, and other things, he did not allow them except in cases on dire necessity:
( غير باغ ولا عاد )
“Not in disobedience, nor in transgression” 
And in another Verse:
( فمن اضطر في مخمصة غير متجانف لإثم فإن الله غفور رحيم )
“As for someone who is forced by severe hunger, with no inclination towards sin, then verily Allaah is All-Forgiving, Ever Merciful.” 
It is well known that someone using a medical treatment (to treat an ailment) is not forced by dire necessity to use it (i.e. it is not obligatory for him to use it). Thus, it is known that it does not ever become permissible for him.
Regarding things that are permissible for certain needs less than absolute necessity, like the wearing of silk, then it has been authentically reported in the Saheeh collections [of al-Bukhaaree and Muslim] that the Messenger of Allaah (may Allaah raise his rank and grant him peace) allowed Az-Zubayr and ‘Abdur-Rahmaan ibn ‘Owf to wear silk, due to a skin condition they had. 
This is something permissible according to the more correct opinion of the two positions held by the scholars, since wearing silk has only been forbidden (for men) due to the lack of need for it and the availability of many other materials. This is why it is allowed for women, as they need it to beautify themselves with it, and thus they have been allowed to use it to cover themselves with it as clothing in general. So to use it as a medical treatment is acceptable for an even more important reason. It has only been forbidden due to the extravagance, arrogance, and (false) bragging that commonly comes with it (among men). Once a person is in need of it, these things do not manifest in him.
Similary would be the idea of wearing it (silk) in cold weather or when a person has nothing else to wear. 
Source: Majmoo’ al-Fataawee (24/272-276).
Translated by: Moosaa Richardson
 Waa’il ibn Hujr: Aboo Hunaydah al-Kindee, A revered companion from the lineage of the kings of Yemen.
 Taariq ibn Suwayd al-Ju’fee: A respected companion from Hadramout, Yemen, he was referred to as “Suwayd ibn Taariq” (backwards) sometimes.
 Saheeh Muslim (#1984)
 Sunan Abee Daawood (#3874), with a weak chain of narration, however its meaning is supported in the many other narrations in this passage.
 Musnad Ahmad (2/305), Sunan Abee Daawood (#3870), Jaami’ At-Tirmithee (#2045), Sunan Ibn Maajah (#3459). Al-Albaanee called it saheeh.
 ‘Abdur-Rahmaan ibn ‘Uthmaan: at-Taymee, honored companion, one of Talhah’s cousins.
 Musnad Ahmad (3/453), Sunan Abee Daawood (#3871, #5279), and Sunan an-Nasaa’ee (#4355). Al-Albaanee called it saheeh.
 Saheeh al-Bukhaaree (right before #5614).
 Saheeh Ibn Hibbaan (#1391 of Ibn Bulbaan’s re-ordering), on the authority of Umm Salamah (may Allaah be pleased with her). The chain is weak, and it seems that the narration is more correctly attributed to Ibn Mas’ood as his statement.
 Saheeh Muslim (#2003). A different wording was collected by Aboo Daawood and at-Tirmithee: “Whatever intoxicates by the ‘faraq’ (container) is haraam by the handful.” In one of the wordings collected by at-Tirmithee: “Then one sip of it is haraam.” It was called saheeh (authentic) by Al-Albaanee in Irwaa’ al-Ghaleel (no.2376). According to Ibn al-Atheer in his famous dictionary of hadeeth terminology (An-Nihaayah), a “faraq” (container) is 3 saa’s, or 2.5 according to some measurements. In modern day equivalencies, 2.5 saa’s is about 7.5 litres, and 3 saa’s is about 9 litres.
 Saheeh al-Bukhaaree (#5586) and Saheeh Muslim (#1733)
 Saheeh al-Bukhaaree (#4344, #4345) and Saheeh Muslim (#2001)
 Saheeh Muslim (#2002)
 Soorah al-Baqarah :173
 Soorah Al-Maa’idah :3
 Saheeh al-Bukhaaree (#2921, #2922, #5839) and Saheeh Muslim (#2076)
 Shaykh al-Islaam Ibn Taymiyyah has other more detailed words on related topics as well. In his time, marijuana was from the generality of smoked intoxicants called “sheeshah” (الشيشة), and it later became specifically identified as “al-Qanab al-Hindee” (القنب الهندي), or Indian Cannabis.
He actually considered herbal (smoked) intoxicants like marijuana to be worse than alcoholic drinks from a number of angles, and he felt that the calamities of Genghis Khan and the Mongols only befell the Muslims once they openly accepted the use of herbal (smoked) intoxicants widely in the late sixth and early seventh centuries. (Review: Majmoo’ al-Fataawee, 34/204-214)