Musannaf Ibn Abi Shaybah

Hazrat Abu Saeed Khudri (may Allah be pleased with him) narrates that it is not permissible for anyone to use the milk of someone’s she-camel without permission if the teats of that she-camel have been tied. Indeed, tying its teats is its seal (i.e., now it cannot be used). And if people (a group) run out of provisions and become destitute, then call the shepherd three times; if he responds to your call, then take from him and drink. Otherwise, two people should seize it and milk it to drink.