Sayyiduna Samurah (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) (and Musa, in another place, said: from Samurah, as far as Hammad thought) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever comes to own a mahram relative, that relative is free."
Abu Dawud said: No one narrated this hadith except Hammad bin Salamah, and he had doubt about it. Abu Isa al-Tirmidhi said, according to what reached me from him: I asked al-Bukhari about this hadith, and he did not know it from al-Hasan from Samurah except as the hadith of Hammad bin Salamah. Al-Shaykh (al-Bayhaqi) (may Allah have mercy on him) said: Hammad was in doubt about mentioning Samurah in its chain, as we mentioned earlier from Musa bin Isma'il; others besides Hammad narrate it from Qatadah from Umar bin al-Khattab (may Allah be pleased with him), and from Qatadah from al-Hasan as his own saying.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21416