Brachos 5:3-4

Brachos 5:3

If the person reciting Shemoneh Esrei ad libs that G-d’s mercy extends to birds’ nests (referring to the mitzvah to shoo away the mother bird before taking the eggs or the young), that we will recall G-d’s Name for the good that He does, or if he doubles the phrase “modim” (“we acknowledge” or “we give thanks”), he should be silenced. (The first two cases, while well-meaning, suggest things that are not theologically accurate. The third case suggests the existence of two powers.) If the one davening makes a mistake in Shemoneh Esrei, he is replaced; the one called upon to replace him should not attempt to decline in such a situation. The replacement starts from the beginning of the bracha where the first reader erred.

Brachos 5:4

This mishna discusses Birkas Kohanim, AKA the Priestly Benediction, AKA “duchening.” The one repeating Shemoneh Esrei should not recite “amen” after the blessings of the kohanim because he might get confused. If he is the only kohein present, he should not duchen. If he is confident that he will be able to duchen and then resume Shemoneh Esrei without incident, then he may.