Forbidden trades and lawful career change

Trading what Allah has forbidden

Wine: forbidden to sell by consensus: "Allah and His Messenger have forbidden the sale of wine, carrion, swine and idols" (al-Bukhari 2121, Muslim 1581); "He who forbade drinking it forbade selling it" (reported by Malik in the Muwatta 1543); Ibn Abd al-Barr, Ibn al-Mundir and al-Qurtubi report the agreement of all. Swine and carrion: the same prohibition by consensus (sura al-Ma'ida 3; Ibn al-Mundir, an-Nawawi); the price of swine is haram, all parts included (Ibn al-Qayyim, Ibn Kathir). Blood: "the Prophet forbade the price of blood and the price of a dog" (al-Bukhari 2123); the scholars agree on forbidding its sale, the liver and the spleen remaining lawful to eat (reported by Ahmad 5723, Ibn Majah 3314).

Idols, crosses and instruments

Selling idols is forbidden by consensus; Ibn al-Mundir excepts idols of gold, silver, iron or lead once melted and turned into vessels or pieces. al-Bagawi draws from it the prohibition of selling any crafted image and any instrument of unlawful amusement (drum, flute, instruments), their materials becoming sellable again once transformed; Ibn al-Qayyim adds the books of shirk, to be destroyed, their sale opening the way to owning them.

Weapons

• Selling weapons amid discord among Muslims: forbidden for the Hanafis, Malikis and Hanbalis when the buyer will fight with them (cooperation in sin, sura al-Ma'ida 2; the hadith of Imran ibn Husayn is judged weak by specialists); the Shafi'is discourage without invalidating the sale (ash-Shafi'i's view in the Umm: the prohibition is presumptive, the weapon possibly serving jihad).
• Selling weapons to the enemy at war: forbidden by consensus (an-Nawawi): weapon, mount, or anything strengthening the enemy against the Muslims.
• Selling to rebels and brigands: forbidden for the Hanafis, Malikis and Hanbalis; discouraged yet valid for the Shafi'is; selling to the people of justice to fight the rebels remains allowed.

The debated cases: dog and cat

The trained hunting dog: its price is accepted by the Hanafis (report from Ibrahim, a Prophetic license); void for the Shafi'is and Hanbalis (hadith of Abu Mas'ud, al-Bukhari 2237, Muslim 1567); among the Malikis, the forbidden dog is not sold by agreement, the hunting dog dividing opinions. The price of the cat is not unlawful but lowly per at-Tahawi; the jumhur accepts it (Ibn Rushd), Ibn al-Qayyim preferring prohibition on Jabir's report. The rule arising: what may not be sold carries no compensation upon its destroyer.

The way back

These prohibitions guard the body, the mind and the faith. Leaving a forbidden trade means replacing the object lawfully, not disguising it: such is the thrust of the Prophetic order to do away with wine rather than price it.

Practical note

A simple grid: is the object unlawful in itself? does my part directly serve the unlawful? The fuqaha's answer is constant for wine, swine, blood, carrion, idols and arming the enemy.