Musannaf Ibn Abi Shayba 18:21

Abu Bakr narrated to us, he said: Muhammad ibn Bakr narrated to us, from Ibn Jurayj, who said: I said to ‘Ata’, "If the wealthy person wishes, he may give one hundred camels, or two hundred cows, or two thousand sheep, and not give gold." He said: "If he wishes, he may give camels and not give gold." He said: ‘Ata’ said: "It used to be said: upon the people of camels is camels, and upon the people of cows is cows, and upon the people of sheep is sheep."