Sunan Ibn Majah, Chapter: The Chapters on Business Transactions

"While we were with the Messenger of Allah (saw) on a journey, we saw some camels with their udders tied, among some thorny trees. We rushed towards it, but the Messenger of Allah (saw) called us and we came back to him. He said: 'These camels belong to a family of Muslims, and this is their support (and blessing) after Allah. Would you be happy if you went back to your vessels and found that what was in them had been taken away? Do you think that is fair?' They said: 'No.' He said: 'This is like that.' We said: 'What do you think if we are in need of food and drink?' He said: 'Eat but do not carry any away: drink but do not carry any away."'