Yahya related to me from Malik that he had heard that Umar ibn al-Khattab said, "There is no hoarding in our market, and men who have excess gold in their hands should not buy up one of Allah's provisions which he has sent to our courtyard and then hoard it up against us. Someone who brings imported goods through great fatigue to himself in the summer and winter, that person is the guest of Umar. Let him sell what Allah wills and keep what Allah wills."

Muwatta Malik Book 31, Hadith 56