Silsilah as-Sahihah 3430 — Why is the believer likened to a date palm?

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "There is a tree whose leaves do not fall, the example of the believer is like that tree. Tell me, which tree is it?" The people began to think about the various trees of the forest. Sayyiduna Abdullah (may Allah be pleased with him) says: I thought it was the date-palm tree, but I was shy to say it. Eventually, the companions said: O Messenger of Allah! Please explain it yourself. The Prophet (peace and blessings be upon him) said: "It is the date-palm tree."