Reference for Bekhorot 84:41
דתנן רבי יהודה אומר
and according [to the Tanna in the Baraitha] who holds: The wife of a tumtum must be released by halizah but must not marry his brother, we maintain that since the status has changed, he is a different person!<span class="x" onmousemove="('comment',' In case he is a born saris, even if he be a male. She therefore cannot marry her deceased husband's brother, for as he is as male, the betrothal is valid, but since he is a born saris, his wife is not subject to yibbum. She is therefore like a woman who has children and the brother would be marrying a sister-in-law of that status, this being one of the forbidden marriages of consanguinity. Halizah, however, would be necessary, in case he is not a saris.');"><sup>29</sup></span>