Musannaf Ibn Abi Shayba 20:14

Abu Bakr narrated to us, he said: Yazid bin Harun narrated to us, from Mahdi bin Maymun, from Muhammad bin Abi Ya'qub, from al-Hasan bin Sa'd, he said: Rabah narrated to me, from Uthman, that the Messenger of Allah, may Allah bless him and grant him peace, decreed that the child belongs to the bed.