He will say to one person three times peace be upon you.
Sources: Even though it was customary to say to G. Bani Adam as the Mash Hamata Moshe C. 1900, mm the main custom in its origin was to say to one person 3 times peace be upon you, the trinity is multiplied only for the purpose of the saying like the other things that are multiplied 3 times, but not precisely As for the 3rd Bani Adam, it is the same in the Book of Scribes 19 and in the Rama'a Och 10 72, and also in the Meta Moshe there he wrote that if he does not have three people, he will say to one person.
And there is a basis for the custom of saying to G-d's people that in this it makes them like a power in the 4th to bless and make peace, as we found regarding the benefit of a dream [Barchot Na 12] that says three peace to G-d's people.
ויש לציין בזה גם לדברי הגמ' בנדרים לגבי מי שחלם דליזיל לפרשת דרכים ולומר שלום לבי עשרה עי"ש במפרשים.
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