Musannaf Ibn Abi Shayba 3:2301

Ali ibn Ishaq narrated to us, from Ibn al-Mubarak, from al-Awza'i, who said: Yahya ibn Abi Kathir narrated to us, from Abdullah ibn Abi Qatadah, from his father, that the Prophet, peace and blessings of Allah be upon him, said: "Indeed, I am in the prayer and I intend to prolong it, then I hear the crying of a child, so I shorten the prayer, disliking to cause hardship to his mother."