It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "No one should milk another's animal without his permission. Would any of you like that someone comes into his storeroom, breaks open his treasure, and takes away his food grain? So, the udders of their animals safeguard their food milk, meaning the udders are for protection just like a storeroom is for protection. Therefore, no one should ever milk another's animal without his permission."