Sahih Bukhari Volume 003, Book 049, Hadith Number 873.
Narated By Abdullah bin Kab : That Ka'b bin Malik told him that in the lifetime of Allah's Apostle he demanded his debt from Ibn Abu Hadrad in the Mosque. Their voices grew louder till Allah's Apostle heard them while he was in his house. So he lifted the curtain of his room and called Ka'b bin Malik saying, "O Ka'b!" He replied, "Labbaik! O Allah's Apostle!" He beckoned to him with his hand suggesting that he deduct half the debt. Ka'b said, "I agree, O Allah's Apostle!" Allah's Apostle then said (to Ibn Abu Hadrad), "Get up and pay him the rest."