It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "If an animal is kept with someone as collateral, its fodder will be obligatory upon the one holding it, and the milk of a milking animal can be drunk, but whoever drinks its milk, its expense will also be upon him, and it can also be ridden."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7125