Role in the film
The Forty Thieves are a group of notorious bandits led by their chief Cassim and his second-in-command Sa'Luk, where they stole lots of beautiful treasure given as gifts for Aladdin and Jasmine during the wedding including the Oracle's Scythe.
Despite their ruthless behavior using weapons to steal, they are not seen inflicting any physical harm against innocent people, as Cassim himself already wrote up a new rule in their code while becoming their leader: never harm the innocent, in which the Forty Thieves would have to keep to stay in touch with their group. There were originally forty thieves, hence the name Forty Thieves. However, due to the betrayal of Sa'Luk (who informed the location to Razoul after being replaced by Aladdin during a fight between him), 31 of the Thieves got arrested and somehow seven of them managed to evade them (either they hid or they weren't present when Razoul's men arrived to the cave), among them being Behrang, Faizullah, Omid, Mujahideen, and the Three Twin Thieves.
The arrested 31 Thieves vow that Sa'Luk will pay for his betrayal, even when Sa'luk closes the door on them. Upon returning to the hideout, Sa'Luk then lies to the remaining seven thieves that it was Cassim who was responsible for betraying them and convinced them to mutiny against him.
Eventually, in an act of justice during the climax, Sa'Luk ended up being turned to a golden statue by the Hand of Midas as punishment, as well as the seven thieves having turned their boat into solid gold, sinking the boat, leaving them alone in the middle of the seas with no boat to return to shore. It was unknown if they survived or not.
Omid: Another raid?!
Three Twin Thieves: Not again...
Mujahideen: It is a good day to die...
Sa'luk: Or to come back from the dead.
Three Twin Thieves: You're alive?!
Faizullah: Impossible!—Sa'luk surprises the remaining thieves with his survival after being presumed dead after his fight with Aladdin
- During the song "Friend Like Me" of the original Aladdin, the Genie aids Aladdin on defeating some thieves from the Forty Thieves by punching them away. This rendition of the Forty Thieves isn't the same seen in the third film. While it's obvious that both iterations of the Thieves are different because the story for Aladdin and the King of Thieves wasn't planned yet, an in-universe explanation could be that these members were former members of the gang and were replaced or they were other groups of Forty Thieves. However, in King of Thieves, Genie mentions that the amounts of Thieves don't add up to 40, meaning it's likely that the Thieves from the first movie simply never appeared during the events of King of Thieves.