The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1108
Abu Qatada al-Ansari reported: I saw the Apostle (may peace be upon him) leading the people in prayer with Umima, daughter of Abu'l-'As and Zainab, daughter of the Apostle of Allah (may peace be upon him), on his shoulder. When he bowed, he put her down, and when he got up after prostration, he lifted her again.