Musnad Ahmad 27:1204

Qurrad Abu Nuh narrated to us, Ubaydullah ibn Umar informed us, from Nafi’, from Ibn Umar, who said: The Prophet (peace and blessings of Allah be upon him) said: "There is no *jalab* (bringing livestock to the market to sell them at a lower price than the market rate), no *janab* (the tax collector staying away from the people's homes to collect zakat), and no *shighar* (a type of marriage where a man gives his daughter in marriage to another man on the condition that the other man gives his daughter to him in marriage, without a dowry) in Islam."