Maliks Muwatta Book 49, Hadith Number 29.
Section : General Section on Food and Drink.
Yahya related to me from Malik from Yahya ibn Said that Umar ibn al-Khattab was eating bread with ghee. He summoned one of the desert people and he began to eat and follow the grease in the dish with a morsel of bread. Umar said, “It is as if you were poor.” He said, “By Allah. I have not eaten ghee nor have I seen food with it since such-and-such a time.” Umar declared, “I shall not eat clarified butter until people are given life again like they were first given life.” (i.e. on the Day of Rising.)