Sunayn Abu Jamilah narrated to Sa'id bin al-Musayyib (may Allah have mercy on him), saying: I found an abandoned child in the time of Sayyiduna Umar (may Allah be pleased with him). My overseer ('arif) mentioned it to Sayyiduna Umar (may Allah be pleased with him), so he sent someone to me and summoned me, and the overseer was also there. When he saw me coming, he said: Is this the one? 'Perhaps the little cave holds misfortune' (i.e. perhaps there is something behind this). The overseer said: O Commander of the Believers! He is not under suspicion. He said: Why did you take him? I said: I saw a life being lost, and I hoped that Allah would reward me. He said: He is free, his wala' is yours, and his nursing (upbringing) is our responsibility.
Imam al-Shafi'i (may Allah have mercy on him) replied to it that this is not the kind of report that is established, since it comes from a man who is not known, meaning Abu Jamilah. He then carried his argument on to show that the Sunnah is that the wala' belongs to the one who frees, that a hadith of the Prophet (peace and blessings be upon him) may remain hidden from some of his Companions, and that no one's view carries authority against the Prophet (peace and blessings be upon him), even if they are many.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الولاء / 21468