Hoda’ah: Rashi & The Rishonim
The Modim D’Rabbanan – the Modim we recite during the repetition of the Amidah – ends with a strange phrase, “That we thank You.” Why do we thank God for the fact that we thank Him?
Rashi reads this as, “We thank You for inspiring us to attach to You and to acknowledge all You do for us. (Sotah 40a)
Tosafot: The Aruch, in the section on Hoda’ah, quotes Rav Moshe, Rosh Yeshiva, that we are declaring that we are joining with the Chazan as he recites Modim. “We are all thanking You!”
Rabbi Yosef Ibn Migash: We are not satisfied with the gratitude we expressed in our Amidah, and want to add to – “al” – on top of – what we have already included in our thanks. Hoda’ah is a constant, and should always be accompanied by a sense of I can never adequately declare my gratitude.