Sahih al-Bukhari 62

Khalid ibn Makhlad narrated to us. He said: Sulayman narrated to us. He said: Abdullah ibn Dinar narrated to us, from Ibn Umar, from the Prophet (peace and blessings be upon him), who said: ‘Among the trees there is a tree whose leaves do not fall, and it is like a Muslim. Tell me, what is it?’ He said: The people began naming the trees of the open country. Abdullah said: It occurred to me that it was the date palm. Then they said: ‘Tell us what it is, Messenger of Allah.’ He said: ‘It is the date palm.’