Sayyidah Aishah (may Allah be pleased with her) says: The Messenger of Allah (peace and blessings be upon him) bought a camel from a Bedouin for one wasq of Ajwah dates. He (peace and blessings be upon him) had his household checked for dates, but there was nothing in the house, so he (peace and blessings be upon him) told the Bedouin that the dates could not be found for now. The Bedouin cried out: "Alas, treachery!" The Companions replied to him: "O enemy of Allah! You are the treacherous one." The Messenger of Allah (peace and blessings be upon him) said: "Leave him, for the one who is owed something speaks this way." The Messenger of Allah (peace and blessings be upon him) sent one of his men to Khawlah bint Hakim (may Allah be pleased with her), and sent the Bedouin along with him. He (peace and blessings be upon him) told his messenger to say to Khawlah: "I have bought this camel from this Bedouin for one wasq of Ajwah dates, and no dates were found in my house; give this Bedouin one wasq of Ajwah dates on my behalf as a loan (salaf)." So when the Bedouin had received his due, he returned to him (peace and blessings be upon him). The Messenger of Allah (peace and blessings be upon him) asked: "Did you receive the dates?" He said: "Yes! You have given the full measure." The Messenger of Allah (peace and blessings be upon him) said: "Those are the best of people who fulfil their promise in full and give the full measure."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11095