Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Sayyiduna Abu Qatadah Al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to perform prayer while carrying his granddaughter Umamah bint Zaynab (may Allah be pleased with her), who was the daughter of Abu Al-As ibn Al-Rabi’ ibn Abd Shams. When he would go into prostration, he would put her down (on the ground), and when he stood up, he would pick her up. Imam Malik said: This action was in voluntary prayers.