Musannaf Ibn Abi Shayba 33:239

Abu Khalid al-Ahmar narrated to us, from Yahya ibn Sa'id, from Muhammad ibn Yahya ibn Habban, who said: There was a platter in front of Umar containing crumbled bread with fat in it. A man came who looked like a Bedouin, so Umar said, "Eat." He began to follow the fatty morsels on the side of the platter. Umar said, "It is as if you are famished." He replied, "By Allah, I have not tasted ghee, nor have I seen anyone eating it." Umar said, "By Allah, I will not taste ghee until the people live from the first of what they live upon."