Sahih Bukhari Volume 001, Book 008, Hadith Number 460.
Narated By 'Kab bin Malik : During the life-time of Allah's Apostle I asked Ibn Abi Hadrad in the mosque to pay the debts which he owed to me and our voices grew so loud that Allah's Apostle heard them while he was in his house. So he came to us after raising the curtain of his room. The Prophet said, "O Ka'b bin Malik!" I replied, "Labaik, O Allah's Apostle." He gestured with his hand to me to reduce the debt to one half. I said, "O Allah's Apostle have done it." Allah's Apostle said (to Ibn Hadrad), "Get up and pay it."