Musnad Abu Ya'la al-Mawsili 209:97

Abu Khaythama narrated to us, Abd al-Rahman narrated to us, Wuhayb narrated to us, from Khalid, from Abu Qilabah, from Zaynab bint Umm Salamah, from Umm Salamah, who said: My bedding was at the place of prayer of the Messenger of Allah, may Allah bless him and grant him peace. He would pray while I was beside him.