Mishnayos Gittin Perek 2 Mishnah 3

One may write a bill of divorce with any material that can be used for writing: With deyo, with paint [sam], with sikra, with komos, with kankantom or with anything that produces permanent writing. However, one may not write with other liquids, nor with fruit juice, nor with anything that does not produce permanent writing. Similarly, with regard to the document itself, one may write on anything, even on an olive leaf, or on the horn of a cow. And the latter is valid if he gives her the entire cow. Likewise, one may write a bill of divorce on the hand of a slave, and that is valid if he gives her the slave. Rabbi Yosei HaGelili disagrees and says: One may not write a bill of divorce on any living thing, nor may it be written on food.

בַּכֹּל כּוֹתְבִין, בִּדְיוֹ, בְּסַם, בְּסִקְרָא, וּבְקוֹמוֹס, וּבְקַנְקַנְתּוֹם, וּבְכָל דָּבָר שֶׁהוּא שֶׁל קְיָמָא. אֵין כּוֹתְבִין לֹא בְמַשְׁקִים, וְלֹא בְמֵי פֵרוֹת, וְלֹא בְכָל דָּבָר שֶׁאֵינוֹ מִתְקַיֵּם. עַל הַכֹּל כּוֹתְבִין, עַל הֶעָלֶה שֶׁל זַיִת, וְעַל הַקֶּרֶן שֶׁל פָּרָה, וְנוֹתֵן לָהּ אֶת הַפָּרָה, עַל יָד שֶׁל עֶבֶד, וְנוֹתֵן לָהּ אֶת הָעָבֶד. רַבִּי יוֹסֵי הַגְּלִילִי אוֹמֵר, אֵין כּוֹתְבִין לֹא עַל דָּבָר שֶׁיֵּשׁ בּוֹ רוּחַ חַיִּים, וְלֹא עַל הָאֳכָלִין: