Musnad Ahmad 1060:16

Yahya narrated to us, Rushdin narrated to us, Huyayy ibn Abdullah—a man from Yahsab—narrated to me, from Abu Abd al-Rahman al-Hubuli, from Abu Ayyub al-Ansari, from the Messenger of Allah (may Allah bless him and grant him peace) that he said: "Whoever separates between a child and his parent in a sale, Allah will separate between him and his loved ones on the Day of Resurrection."