Musnad Abi Ya'la 5254 — he said: Whoever buys a milk animal whose milk

It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that he said: "Whoever buys a milk animal whose milk has been held back (in its udders in order to deceive), and then returns it (on discovering the defect), should return a sa' along with the animal (in exchange for the milk he used)." And he said: "The Prophet (peace and blessings be upon him) forbade going out to meet (those bringing) trade goods (before they reach the market)."