Musnad Ahmad 32:1419

Hashim narrated to us, al-Mubarak narrated to us, from al-Hasan, from Anas ibn Malik, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) would deliver the sermon on Friday, he would lean his back against a wooden post. When the people became numerous, he said, "Build me a pulpit," intending for them to hear him. So they built him two steps, and he moved from the wooden post to the pulpit. Anas ibn Malik informed me that he heard the wooden post moaning with the moaning of a bereaved mother. He said: It did not cease moaning until the Messenger of Allah (peace and blessings of Allah be upon him) descended from the pulpit, walked to it, and embraced it, whereupon it became silent.