Abdullah bin Ka'b bin Malik narrates from his father (may Allah be pleased with him) that he demanded repayment of his debt from Abdullah bin Abi Hadrad (may Allah be pleased with him) in the Prophet's Mosque, and their voices became raised until the Messenger of Allah (peace and blessings be upon him) heard them from his chamber. He (peace and blessings be upon him) drew back the curtain, came out and said: "O Ka'b, reduce your debt by this much." He (peace and blessings be upon him) gestured to waive half. Ka'b (may Allah be pleased with him) said: Yes, O Messenger of Allah. Then the other man paid the rest.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلح / 11345