Musnad Ahmad 30:642

'Abd al-Razzaq narrated to us, from Ma'mar, from al-Zuhri, from Ibn al-Musayyib—thus he said—from Abu Hurayrah, who said: A man from the Fazari tribe came and mentioned a hadith to the Prophet, peace and blessings of Allah be upon him, and said: "My wife has given birth to a black boy," and he was at that time hinting at disowning him. The Messenger of Allah, peace and blessings of Allah be upon him, said: "Do you have camels?" He said: "Yes." He said: "What are their colors?" He said: "Red." He said: "Are there any ashen-colored ones among them?" He said: "Yes, there are some ashen ones among them." He said: "From where do you think that came?" He said: "I do not know; perhaps it is a strain (gene) that pulled them." He said: "And this, perhaps it is a strain that pulled him." And he did not grant him permission to disown him.