Musannaf Ibn Abi Shayba 9:1260

Abu Usama narrated to us, from Hisham, from Hafsa, who said: When my father married Sirin, he invited the companions of the Messenger of Allah (may Allah bless him and grant him peace) for seven days. When the day of the Ansar arrived, he invited them, and he invited Ubayy ibn Ka'b and Zayd ibn Thabit. Hisham said: And I think he said Mu'adh. She said: My father was fasting. When they had eaten, Ubayy ibn Ka'b made supplication, and the people said 'Amin'.