Musannaf Ibn Abi Shayba 27:371

Mu'tamir ibn Sulayman narrated to us, from his father, who said: I heard al-Hasan saying: Umar and al-Mughirah ibn Shu'bah proposed to a woman. They married her to al-Mughirah and rejected Umar. He said: And they said, "Reject Umar." He said: The Prophet of Allah, may Allah bless him and grant him peace, said: "They have left or rejected the best of this nation."