Musannaf Ibn Abi Shayba 9:1438

Ibn ‘Ulayyah narrated to us, from Yunus, from al-Hasan, from his father, that ‘Umar proposed to ‘Ali for his daughter, Umm Kulthum. ‘Ali said, "She is young, so look at her." He sent her to him with a message, and he (Umar) joked with her. She said, "Were it not that you are an old man, or were it not that you are the Commander of the Faithful..." ‘Umar was pleased with the marriage alliance, so he proposed for her, and he (Ali) married her to him.