Musnad Ahmad 30:1496

Surayj narrated to us, Abu Ma'shar narrated to us, from Muhammad ibn 'Amr ibn 'Alqamah, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever hoards goods, intending by it to raise prices for the Muslims, he is a sinner."