Musnad Abu Ya'la al-Mawsili 209:96

Abu Khaythama narrated to us, Abd al-Rahman narrated to us, Sufyan narrated to us, from Ammar al-Duhni, from Abu Salamah, from Umm Salamah, that the Prophet (peace and blessings of Allah be upon him) said: "The legs of the pulpit are fixed in Paradise."