عَن الْحسن عَن سَمُرَة عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «من ملك ذَا رحم محرم فَهُوَ حُرٌّ» . رَوَاهُ التِّرْمِذِيُّ وَأَبُو دَاوُدَ وَابْنُ مَاجَه

Ibn ‘Abbas reported the Prophet as saying, “When a man’s slave-woman bears him a child she becomes free at his death.”* Darimi transmitted it.* The text has 'au durbur in minhu au ba'dahu’ indicating a doubt on the part of a transmitter as to which words were used. Both expressions amount to the same thing so it seems sufficient to give "at his death" in the translation above.