Sunan Abi Dawud, Book 23, Hadith 3527 (USC-MSA) ⓘ

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 say: Pay the deposit to him who deposited it with you, and do not betray him who betrays you.

حَدَّثَنَا أَبُو كَامِلٍ، أَنَّ يَزِيدَ بْنَ زُرَيْعٍ، حَدَّثَهُمْ حَدَّثَنَا حُمَيْدٌ، - يَعْنِي الطَّوِيلَ - عَنْ يُوسُفَ بْنِ مَاهَكَ الْمَكِّيِّ، قَالَ كُنْتُ أَكْتُبُ لِفُلاَنٍ نَفَقَةَ أَيْتَامٍ كَانَ وَلِيَّهُمْ فَغَالَطُوهُ بِأَلْفِ دِرْهَمٍ فَأَدَّاهَا إِلَيْهِمْ فَأَدْرَكْتُ لَهُمْ مِنْ مَالِهِمْ مِثْلَيْهَا ‏.‏ قَالَ قُلْتُ أَقْبِضُ الأَلْفَ الَّذِي ذَهَبُوا بِهِ مِنْكَ قَالَ لاَ حَدَّثَنِي أَبِي أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ أَدِّ الأَمَانَةَ إِلَى مَنِ ائْتَمَنَكَ وَلاَ تَخُنْ مَنْ خَانَكَ ‏" ‏ ‏.‏