Musannaf Ibn Abi Shayba 17:1322

Abu Bakr narrated to us, he said: Yahya ibn Adam narrated to us, he said: Ibrahim ibn Sa'd narrated to us, from al-Zuhri, from Ubayd Allah, from Ibn Abbas, he said: The Messenger of Allah (may Allah bless him and grant him peace) was the most generous of people with goodness, and he was at his most generous when Gabriel would meet him.