Musnad Ahmad 26:575

Waki’ narrated to us, al-Mas’udi narrated to us, from Jabir, from Abu al-Duha, from Masruq, from ‘Abdullah, who said: The Messenger of Allah (ﷺ) narrated to us, and he is the truthful, the believed: "The selling of *muhaffalat* (animals whose milk has been withheld in the udder to deceive the buyer) is *khulabah* (deception), and *khulabah* is not lawful for a Muslim."