It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: 'Man malaka dha rahimin mahramin fa-huwa 'atiq' "Whoever becomes the owner of a relative whom it is unlawful (to marry), that relative is free."
Sulayman (may Allah have mercy on him) said that no one narrated this hadith from Sufyan (may Allah have mercy on him) except Damrah. The Shaykh (may Allah have mercy on him) said: The preserved (mahfuz) hadith with this chain is the one about 'Naha 'an bay' al-wala' wa 'an hibatihi' "(The Prophet (peace and blessings be upon him)) forbade selling wala' and giving it as a gift", and Abu Umayr did narrate it from Damrah, from al-Thawri, together with the first hadith. [Munkar]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21419