Musannaf Ibn Abi Shayba 26:521

Ibn ‘Ulayyah narrated to us, from Ibn ‘Awn, from al-Hasan, that he used to say: "If a man is emancipated, and another man emancipates his son, the son draws the *wala’* (patronage) of his father." Muhammad ibn Sirin came to him and said: "Umar says this?" He replied: "We say it."