Mishnayos Gittin Perek 7 Mishnah 1

In the case of one who was afflicted with temporary insanity [kordeyakos] and said: Write a bill of divorce for my wife, he said nothing, because he was not lucid at the time. If he said: Write a bill of divorce for my wife, when he was lucid, and was then afflicted with temporary insanity and he retracted his previous statement and said: Do not write it, his latter statement is considered to be nothing, i.e., it is not halakhically valid. The mishna continues: In a case where the husband became mute, and two people said to him: Shall we write a bill of divorce for your wife, and he nodded his head indicating his agreement, they examine him with various questions three times. If he responded to questions that have a negative answer: No, and responded to questions that have a positive answer: Yes, indicating his competence, they shall write the bill of divorce and give it to his wife based on the nod of his head.

מִי שֶׁאֲחָזוֹ קֻרְדְּיָקוֹס, וְאָמַר, כִּתְבוּ גֵט לְאִשְׁתִּי, לֹא אָמַר כְּלוּם. אָמַר, כִּתְבוּ גֵט לְאִשְׁתִּי, וַאֲחָזוֹ קֻרְדְּיָקוֹס, וְחָזַר וְאָמַר, אַל תִּכְתֹּבוּ, אֵין דְּבָרָיו הָאַחֲרוֹנִים כְּלוּם. נִשְׁתַּתֵּק, וְאָמְרוּ לוֹ נִכְתֹּב גֵּט לְאִשְׁתֶּךָ, וְהִרְכִּין בְּרֹאשׁוֹ, בּוֹדְקִין אוֹתוֹ שְׁלֹשָׁה פְעָמִים, אִם אָמַר עַל לָאו לָאו וְעַל הֵן הֵן, הֲרֵי אֵלּוּ יִכְתְּבוּ וְיִתֵּנוּ: