Introduction
It is the Jewish custom that upon completing any of the five books of the Torah in our cycle of weekly readings, the entire congregation calls out: ‘Chazak, Chazak, v’Nischazek – Be strong! Be strong! And may we be strengthened!’
Everyone’s Call
‘Chazak, Chazak, v’Nischazek’ is called out by everyone present in the synagogue, including men, women, and children.
Loud and Joyful
We call out with a loud, joyous, voice, which reflects on the strength and steadfastness of the Jewish people in all Torah matters.
Thrice Strengthened
The sources given for this custom in Likutei Sichos, Vol.25 p.474, are: Avudraham, Seder Hatza’os Sefer Torah; Responsa of Maharam Mintz, Chapter 85; Aruch Hashulchan, Orech Chayim, 39:15; Keser Shem Tov (Gagin) Vol.1, 38.
We call out – everyone present in Shul, both those in the men’s section and those in the women’s section and even including young children - ‘Chazak, Chazak, v’Nischazek’, using the word chazak three times. (Parshas Vayechi 5752 – Sichos Kodesh p.505) [In Jewish Law, something done three times constitutes a chazakah (lit. a strength) i.e. a legally valid continuity and power. In this case, the word chazak i.e. the strengthening, is itself given a chazakah (legal strength) by being repeated three times over – Ed.]
Parshas Matos-Masei 5751 – Hisvaduyos p.68.
See there, footnote 4: “Note that the source for this custom is from the fact that ‘When Hashem told Yehoshuah upon the completion of the Torah, ‘Chazak v’Ematz – Be strong and fortified!’ [See footnote 1 above for sources]. The innovation in this custom is that although ‘strength’ is mentioned only twice in the verse, ‘Be strong and fortified’, Jewish custom has nevertheless added a third ‘strength’. Now, in addition to an established Jewish custom being ‘a part of Torah itself’, it even bears an advantage of a kind, over the Written and Oral Torah (See Likutei Torah, Derushei Sukos, 80c and in many other location, for an explanation of this advantage). Moreover, this custom carries the advantage and complete state of ‘something done three times assumes a legal strength, a chazakah’ [See previous footnote].”
