Musnad Ahmad 27:2008

'Umar ibn Sa'd—who is Abu Dawud al-Hafari—narrated to us, Sufyan narrated to us, from 'Abdullah ibn Dinar, from Ibn 'Umar, who said: The Messenger of Allah (ﷺ) said: "Indeed, among the trees is a tree whose leaves do not fall, and it is like the Muslim man." He said: So the people began to speculate about the trees of the desert, and I was among the youngest of the people. It occurred to my heart that it was the date palm. The Messenger of Allah (ﷺ) said: "It is the date palm." He said: So I mentioned that to my father, and he said: "For you to have said that would have been more beloved to me than such and such."