Hazrat Ubayy bin Kaab’s (ra) love for the Holy Prophet (sa) can be gauged from the following incident.
In Masjid al-Nabawi, the Holy Prophet (sa) used to deliver the sermon whilst leaning against the trunk of a date-palm tree that was used a pillar. Later, a pulpit was constructed and when the Holy Prophet (sa) sat on the pulpit to deliver the Friday sermon, a weeping sound resounded from that trunk which was heard by all those that were in the mosque.
The Holy Prophet (sa) went to that trunk and placing his hand over it, he embraced the trunk. The trunk began to weep profusely, just like an innocent child that needs to be consoled and after a while it became content and the noise coming from it stopped. Subsequently when [part of the] mosque was demolished for reconstruction, Hazrat Ubayy (ra) bin Kaab took the trunk home, only because the Holy Prophet (sa) would lean against it. He took the trunk home but later it became withered and was reduced to [wood] dust as termites consumed it. However, he kept the trunk with him owing to his love for the Holy Prophet (sa). This is a narration of Musnad Ahmad bin Hanbal and some parts of it are from Sahih al-Bukhari.
(Musnad Ahmad bin Hanbal, Musnad al-Mukathirin min al-Sahabah, Musnad Jabir Abd-Allah Hadith 14075) (Sahih al-Bukhari, Kitab al-Buyu‘, Bab al-Najjar, Hadith 2095) (Sunan Ibn Majah, Kitab Iqamat al-Salah wa al-Sunnah fiha, Bab ma ja‘a fi Bad’ Sha‘n al-Minbar, Hadith 1414) (Sheikh Shah Moinuddin Ahmad Nadvi, Siyar al-Sahabah, Vol. 3 [Karachi, Pakistan: Dar al-Ishaah Urdu Bazar, 2004] 158)