Gittin 86B

ודוקא כתב ידו ועד; אבל כתב סופר ועד ⁠– לא.

And Rav is saying that specifically when the bill of divorce is written in his handwriting and has the signature of one witness, the woman’s child from her second husband is of unflawed lineage. But if it is written in a scribe’s handwriting, even if it includes the signature of one witness, the child’s lineage is not unflawed, but rather he is a mamzer, as the bill of divorce is completely invalid.

ושמואל אמר: אפילו כתב סופר ועד, שהרי שנינו: כתב סופר ועד ⁠– כשר.

And Shmuel says: Even where it is written in a scribe’s handwriting and it has the signature of a witness, the lineage of the child is unflawed, as we learned in a Mishnah (87b): In the case of a bill of divorce in which the scribe’s handwriting is recognizable and there is one witness signed, it is valid.

ורב ⁠– מי דמי?! התם תינשא לכתחילה, הכא דיעבד.

And Rav would respond: Is that case comparable? There, in that case, the Mishnah indicates that the woman may marry ab initio. Therefore, it must be a case where the scribe also signed as a second witness. But here, in the case of this Mishnah, the bill of divorce is invalid and the woman may not remarry; it is only if she remarried and had a child that his lineage is rendered unflawed after the fact. Therefore, it must be referring to a case where the husband wrote it.

ושמואל ⁠– לא קשיא; הא בספרא דמובהק, והא בספרא דלא מובהק.

And Shmuel, who holds that both cases are referring to a bill of divorce that was written by a scribe but not signed by the scribe as one of the witnesses, would respond that the contradiction is not difficult. That Mishnah, where the bill of divorce is rendered valid ab initio, is referring to the handwriting of an expert scribe, who can presumably be relied upon to have written the bill of divorce properly and only according to the husband’s instructions, and this Mishnah is referring to the handwriting of a scribe who is not expert. Since the bill of divorce was not signed by two witnesses, there is concern that the scribe did not write it properly.