It is narrated from Sayyiduna Sahl bin Sa'd (may Allah be pleased with him); he said: "The Messenger of Allah (peace and blessings be upon him) used to stand by a wooden post (to deliver the sermon). When the number of people grew, the Companions said: 'O Messenger of Allah, the people have grown in number; shall we not make a pulpit for you on which you can stand? For someone comes and finds it hard to go back without hearing anything from you.' So he (peace and blessings be upon him) ordered a slave of the Ansar, and he took tamarisk wood from the forest and made this pulpit for him. When he (peace and blessings be upon him) sat upon it, the wooden post by which he used to stand began to weep (at being parted from him), so he (peace and blessings be upon him) came and placed his hand on it until it fell silent."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5955