(50) باب الْحَيَاءِ فِي الْعِلْمِ
Narrated `Abdullah bin `Umar:
Once Allah's Messenger (ﷺ) said, "Amongst the trees there is a tree, the leaves of which do not fall and is like a Muslim, tell me the name of that tree." Everybody started thinking about the trees of the desert areas and I thought of the date-palm tree but felt shy (to answer). The others asked, "O Allah's Apostle! inform us of it." He replied, "it is the date-palm tree." I told my father what had come to my mind and on that he said, "Had you said it I would have preferred it to such and such a thing that I might possess."
Reference: Sahih al-Bukhari 131
In-book reference: Book 3, Hadith 73
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 3, Hadith 133