Musannaf Ibn Abi Shayba 26:174

Waki’ narrated to us, from Ibn Jurayj, from Ibn Abi Mulaykah, who said: Ibn al-Zubayr said: "The one about whom the Messenger of Allah (peace and blessings of Allah be upon him) said, 'If I were to take a close friend (khalil), I would have taken him,' made the grandfather a father," meaning Abu Bakr.