The Book of Transactions (Kitab Al-Buyu`)
Muslim :: Book 10 : Hadith 3910
Ma'mar (Allah be pleased with him) reported Allah's Messenger (may peace be upon him) as saying: He who hoards is a sinner. It was said to Sa'id (b. al-Musayyib): You also hoard. Sa'id said: Ma'mar who narrated this badith also hoarded.