Aaron Pacanowski asked:
It says in Maseches Berachos that if someone Chas v'Shalom says "Modim Modim Anachnu Lach" we don't let him be Chazan. How come we're allowed to say "Kadosh Kadosh Kadosh . . ."?
Aaron Pacanowski
The Kollel replies:
Kadosh Kadosh Kadosh is a verse (Yeshayah 6:3); each Kadosh of the verse adds a new dimension (as we translate it in u'Va l'Tziyon); it is not just a repetition.
Tosfos (Berachos 34a) makes a similar point regarding "Hash-m Hu ha'Elokim" - we may repeat it seven times since the verse repeats it, and since it is alluding that Hahsem is One in all seven heavens.
Mordecai Kornfeld