I heard the Messenger of Allah ﷺ say, "The worst of earnings are the fee of a prostitute, the price of a dog, and the earnings of a cupper."
سمعت رسول الله ﷺ يقول: شر الكسب مهر البغي، وثمن الكلب، وكسب الحجام.
Muslim reported it in the Book of Sharecropping (1568) from Muhammad bin Hatim, who said, Yahya bin Saeed Qattan told us, from Muhammad bin Yusuf, who said, I heard Saaib bin Yazid narrating from Rafi bin Khadij, who said, and then he mentioned it. In another version, "The price of a dog is foul, the payment for adultery is foul, and the earnings of a cupper are foul." Nasai also reported it in Kubra (4664) through another route from Saaib bin Yazid, who said, the Messenger of Allah said... and continued the hadith. It may be that one of the narrators shortened the chain, making the hadith part of the musnad of Saaib bin Yazid, when in fact the correct view is that he took it from Rafi bin Khadij, and the hadith belongs to his musnad. Abu Hatim Razi also favored this view, in Ilal al-Hadith (1704).As for what is reported from Rafi bin Khadij, who said, "The Messenger of Allah forbade earnings from a slave woman until it is known where they came from," this is daif. Abu Dawud (3427), Hakim (2/42), and Bayhaqi (6/127) all reported it through the hadith of Ibn Abu Fudayk, from Ubaydullah, meaning Ibn Hurayr, from his father, from his grandfather Rafi bin Khadij, who said, and he mentioned the hadith. Ubaydullah is Ibn Hurayr bin Abdul-Rahman bin Rafi bin Khadij, who is mastur (of unclear reliability), and his father Hurayr is majhul (unknown). Hakim did not judge it to be sahih, but rather cited it as corroboration for the hadith of Rafi bin Rifa bin Rafi, in which it is stated, "The Messenger of Allah forbade us from the earnings of a slave woman, except what she earned with her own hand." He said this while gesturing with his fingers toward things like bread-making, spinning, and carding.Ahmad (18998), Hakim, and Bayhaqi (6/126) all reported it through the hadith of Hashim bin Qasim, who said, Ikrima bin Ammar told us, who said, Tariq bin Abdul-Rahman Qurashi told us, who said, Rafi bin Rifa came to the gathering of the Ansar and said, and then he mentioned the hadith, including the other items mentioned. Rafi bin Rifa bin Rafi bin Malik bin Ajlan has not been established to have been a companion, as Ibn Abdul-Barr stated. Tariq bin Abdul-Rahman Qurashi was narrated from only by Ikrima bin Ammar, and no one deemed him reliable except Ibn Hibban and Ajli, both of whom are known to consider unknown narrators reliable. This is why Dhahabi said in al-Mizan, "He is scarcely known."Likewise, what is reported from Abu Umama, that the Messenger of Allah said, "Do not sell singing slave girls, nor buy them, nor teach them, for there is no good in trading them, and their price is forbidden. It was concerning matters like this that this verse was revealed," "Among the people is he who buys distracting talk to lead away from the path of Allah" [Luqman 31:6], is also not sound. Tirmidhi (1282), Ibn Majah (2168), Ahmad (22169), and from him Bayhaqi (6/14–15), and Humaydi (910) all reported it through the route of Ubaydullah bin Zahr, from Ali bin Yazid, from Qasim bin Abdul-Rahman, from Abu Umama, who mentioned it. Ubaydullah bin Zahr and his teacher Ali bin Yazid, who is Ibn Abu Ziyad Alhani, are both daif.Tirmidhi said, I asked Muhammad about the chain of this hadith, and he said, "Ubaydullah bin Zahr is trustworthy, Ali bin Yazid's hadith is worthless, and Qasim Abu Abdul-Rahman is trustworthy." Bukhari said the same about Ubaydullah bin Zahr, though the majority of scholars hold that he is daif.A note, there is a gap in the chain of Ibn Majah between Ali bin Yazid and Abu Umama, where Qasim has dropped out.