It is narrated from Sayyiduna Adi bin Amirah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "O people! Whoever does any work for us and then conceals from us even a needle or anything bigger than it, he is a betrayer; he will come on the Day of Resurrection with that thing (with him)." A dark-skinned man from the Ansar stood up, the narrator says: it is as if I am looking at him now, and he said: "Take back your assignment from me." He (peace and blessings be upon him) said: "Why?" He said: "You have just given a warning about it." So he (peace and blessings be upon him) said: "I say it even now: whomever we appoint over some work, let him bring everything, small and large; what he is given from it he may take, and what he is forbidden from he must refrain from."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13172