Musannaf Ibn Abi Shayba 8:143

Abu Bakr narrated to us, he said: Abdullah bin Numayr narrated to us, from Isma'il, from Wabara, from Ibn Umar, who said: "If a man performs Qiran (combining Hajj and Umrah), then upon him is a sacrificial camel (badana)." It was said to him: "Indeed, Ibn Mas'ud used to say: 'A sheep'." Ibn Umar said: "Fasting is more beloved to me than a sheep."