Related for Kiddushin 151:6
ורבא אמר עבד ושפחה נתערבו בהן איסורא משום מאי משום שפחה ניתני חדא מעשה שהיה כך היה
Then let one [only] be taught?<span class="x" onmousemove="('comment',' E.g., that a mamzer by a sister was mixed up among them.');"><sup>12</sup></span> - The actual event happened thus. Raba said: A [heathen] slave and a bondmaid were mixed up in them.
Tosefta Kiddushin
A female Levite or female Yisrael—[one who seeks to marry them should] add upon them an additional one [generation on both sides that he should investigate to understand their lineage, 1 more than for a female Kohen], which is 12 [people to investigate]. (The following translated from the Ehrfurt manuscript:) If he investigated the mother, he does not need to investigate the children. If he investigated the adults, he does not need to investigate the minors. When does this apply? When [investigating a family that has] one wife. But when [the family has] 2 wives—if he investigated the mother, he needs to investigate the children; and if he investigated the adults, he needs to investigate the minors [because they might be born from different women].
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