חַ֥י חַ֛י ה֥וּא יוֹדֶ֖ךָ כָּמ֣וֹנִי הַיּ֑וֹם אָ֣ב לְבָנִ֔ים יוֹדִ֖יעַ אֶל־אֲמִתֶּֽךָ׃
I vivi, i vivi, ti loderà, come faccio oggi; Il padre dei figli farà conoscere la tua verità.
Rashi on Isaiah
The living, the living This is an expression denoting living people; i.e., when they are living people in the world, this one is living and this one is living, thanksgiving emanates from between them. [Other editions: A living one to a living one You are living, and it is proper to give thanksgiving to a living one.]
Ibn Ezra on Isaiah
The living, the living. The word חי living is repeated as if to say he who is living, as I do, or he who has recovered from illness. Shall praise thee, shall give thanks in words, in which soul and body appear to unite. According to some the first חי refers to God;37The translation of the words חי חי הוא יודך according to this explanation would be: O living God, he who liveth shall praise Thee. but there is no necessity for this assumption.