سنن أبي داود

Narrated Yusuf ibn Malik al-Makki:

I used to write (the account of) the expenditure incurred on orphans who were under the guardianship of so-and-so. They cheated him by one thousand dirhams and he paid these (this amount) to them. I then got double the property which they deserved. I said (to the man: Take one thousand (dirhams) which they have taken from you (by cheating). He said: No, my father has told me that he heard the Messenger of Allah (ﷺ) say: Pay the deposit to him who deposited it with you, and do not betray him who betrays you.