Sahih Bukhari Volume 8, Book 73, Hadith Number 165.

Narated By Ibn ‘Umar : Allah’s Apostle said, “Inform me of a tree which resembles a Muslim, giving its fruits at every season by the permission of its Lord, and the leaves of which do not fall.” I thought of the date-palm tree, but I disliked to speak because Abu Bakr and ‘Umar were present there. When nobody spoke, the Prophet said, “It is the date-palm tree” When I came out with my father, I said, “O father! It came to my mind that it was the date-palm tree.” He said, “What prevented you from saying it?” Had you said it, it would have been more dearer to me than such-and-such a thing (fortune).” I said, “Nothing prevented me but the fact that neither you nor Abu Bakr spoke, so I disliked to speak (in your presence).”