Musannaf Ibn Abi Shayba 20:1

Abu Abd al-Rahman Baqi ibn Makhlad narrated to us, he said: Abu Bakr narrated to us, he said: Sufyan ibn Uyaynah narrated to us, from Ubayd Allah ibn Abi Yazid, from his father, from Umar, that the Messenger of Allah (may Allah bless him and grant him peace) decreed that the child belongs to the bed.