Sahih Bukhari
Virtues and Merits of the Prophet (pbuh) and his Companions
Volume: 004 / Book Number: 056 / Hadith Number: 783
Narrated Ibn Umar:
The Prophet used to deliver his sermons while standing beside a trunk of a datepalm. When he had the pulpit made, he used it instead. The trunk started crying and the Prophet went to it, rubbing his hand over it (to stop its crying).