Gittin 19a
גיטין י״ט א — ד"ה אִיתְּמַר
Gittin 19a:8-10
The Gemara discusses writing over existing writing, including the cases of ink on ink and writing on erased writing, and relates the issue to the writing of a get and to Shabbat. This is the primary sugya underlying R. Chaim's analysis.
אִיתְּמַר: הַמַּעֲבִיר דְּיוֹ עַל גַּבֵּי סִיקְרָא, בַּשַּׁבָּת; רַבִּי יוֹחָנָן וְרֵישׁ לָקִישׁ דְּאָמְרִי תַּרְוַיְיהוּ – חַיָּיב שְׁתַּיִם: אַחַת מִשּׁוּם כּוֹתֵב, וְאַחַת מִשּׁוּם מוֹחֵק. דְּיוֹ עַל גַּבֵּי דְּיוֹ, סִיקְרָא עַל גַּבֵּי סִיקְרָא – פָּטוּר. סִיקְרָא עַל גַּבֵּי דְּיוֹ – אָמְרִי לַהּ: חַיָּיב, וְאָמְרִי לַהּ: פָּטוּר. אָמְרִי לַהּ חַיָּיב – מוֹחֵק הוּא. אָמְרִי לַהּ פָּטוּר – מְקַלְקֵל הוּא. בְּעָא מִינֵּיהּ רֵישׁ לָקִישׁ מֵרַבִּי יוֹחָנָן: עֵדִים שֶׁאֵין יוֹדְעִים לַחְתּוֹם; מַהוּ שֶׁיִּכְתְּבוּ לָהֶם בְּסִיקְרָא, וְיַחְתְּמוּ כְּתָב עֶלְיוֹן? כְּתָב, אוֹ אֵינוֹ כְּתָב? אֲמַר לֵיהּ: אֵינוֹ כְּתָב.
§ It was stated that there was a related discussion about different types of writing: In the case of one who passes ink over letters written in red dye on Shabbat, Rabbi Yoḥanan and Reish Lakish both say that he is liable to bring two sin-offerings for this: One due to violating the prohibition against writing on Shabbat, because he is now writing letters in ink, and one due to violating the prohibition against erasing on Shabbat, because as he writes he erases what is written in red dye. They also agree in the case of ink written on top of ink, or red dye on top of red dye, that according to everyone he is exempt, because he changed nothing with his writing. However, if he wrote with red dye on top of ink, then some say that he is liable and some say that he is exempt. The Gemara explains these opinions: Some say that he is liable because it is erasing, as he erases the higher-quality, original writing. Some say that he is exempt because he is destroying and one who acts destructively is exempt, as he has not performed planned, constructive labor on Shabbat. This dispute pertains to the halakhot of Shabbat. With regard to the signing of documents, Reish Lakish raised a dilemma before Rabbi Yoḥanan: If there are witnesses who do not know how to sign their names, what is the halakha: May their names be written for them with red dye, and afterward they will sign on top of it in ink? The question is: Is the upper writing, which was not directly on the document but on top of other ink, considered to be writing, or is it not writing? He said to him: It is not writing. Consequently, this may not be done for witnesses who do not know how to sign.



