By Horav Yosef Yeshaya Braun, member of the Badatz of Crown Heights
During the Aseres Yemei Teshuva, the Ten Days of Repentance from Rosh Hashana to Yom Kippur, in the third Brocho of Shemonei Esrei, instead of saying Hakeil Hakodosh, we say Hamelech Hakodosh, emphasizing Hashem’s Malchus, kingship, because during these days we see Hashem’s kingship in a more revealed manner.
If a person made a mistake, and instead of saying Hamelech Hakodosh said Hakeil Hakodosh, they need to stop at that point and begin Shemonei Esrei again.
However, if someone remembered right after the words Hakeil Hakodosh, within a time span known as Toich K’dei Dibbur, the amount of time that it takes to say the very quick sentence, “Shalom Alecho, Rabbi”, “Peace upon you, Rabbi”, one can immediately correct themselves by saying the words Hamelech Hakodosh.
If someone has a doubt whether they said the right words, the Halacha is that it is assumed the person said the text to which they are accustomed, which is not the correct one at this time of year, and therefore they would need to repeat the Shemonei Esrei.
However, if at the beginning of the Shemonei Esrei one’s intention was to say the right phrase, and the doubt did not surface immediately at the conclusion of the Shemonei Esrei, but much later, we can assume the person does not remember which one they said, and that they probably said the correct words.