Reference for Arakhin 35:1

ואח"כ מתה בתו פקח ונתחרש וחזר ונתפקח פתוח ונסתמא ואח"כ נתפתח שפוי ונשתטה וחזר ונשתפה כשר

and after that his daughter [the father-in-law's i.e. his wife] died; or if he could hear, became deaf, and no regained his hearing; or if he could see, lost his sight, and now recovered it; or was of sound mind, lost his mind, and now recovered it, then he is eligible [as witness].

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