Reference for Gittin 2:6
קִבֵּל הַקָּטָן וְהִגְדִּיל, חֵרֵשׁ וְנִתְפַּקֵּחַ, סוּמָא וְנִתְפַּתֵּחַ, שׁוֹטֶה וְנִשְׁתַּפָּה, נָכְרִי וְנִתְגַּיֵּר, פָּסוּל. אֲבָל פִּקֵּחַ וְנִתְחָרֵשׁ וְחָזַר וְנִתְפַּקֵּחַ, פָּתוּחַ וְנִסְתַּמֵּא וְחָזַר וְנִתְפַּתֵּחַ, שָׁפוּי וְנִשְׁתַּטָּה וְחָזַר וְנִשְׁתַּפָּה, כָּשֵׁר. זֶה הַכְּלָל, כָּל שֶׁתְּחִלָּתוֹ וְסוֹפוֹ בְדַעַת, כָּשֵׁר:
If the minor received [the get from the husband's hand], and [before he gave it to her] came of age; if he were a deaf-mute, and regained his faculties; if he were blind, and regained his sight; if he were an imbecile and regained his intellect; if he were a gentile, and became a proselyte, it is invalid. But if he possesses his faculties, and then became a deaf-mute, and then regained his faculties; if he possessed sight, and then became blind, and then regained his sight [(it is valid) even if he did not regain his sight. For since he possessed sight when he received the get, he is qualified to be a messenger, being able to say: "Before me, it was written, and before me it was signed." But since we must learn later: "and then he regained his intellect," that he must be of independent intellect at the time of giving, we also learn in the beginning: "and then he regained his sight." And all who are unfit to testify by reason of transgression are not fit to bring the get, not being believed to say: "Before me, it was written, and before me it was signed." And if the get were validated through its signatories, they are fit to bring it.]; if he possessed intellect, and then became an imbecile, and then regained his intellect, it is valid. This is the rule: Wherever there is da'ath (independent intellect) in the beginning and in the end, it (the get) is valid.