The Power of Qaddish
“Rabbi Yehoshua son of Levi said: He who responds [during the recital of Qaddish], ‘May His great Name be blessed forever and eternity’ with all his כֹּחַ (koaḥ), might, his [heavenly] decreed sentence is torn up… Resh Lakish said: He who responds אָמֵן (amen) with all his כֹּחַ (koaḥ), might, has the gates of Paradise opened for him, as it is written, Open the gates, that the righteous nation which keeps the faith, may enter in (Isaiah 26:2)—do not read שֹׁמֵר אֱמֻנִים (shomer emunim), keeps the faith, but שֶׁאוֹמרִים אָמֶן (she’omrim amen), that say, אֶמָן (amen). What does ‘אָמֵן (amen) mean? Rabbi Ḥanina said: אֶל מֶלֶך נֶאֶמָן (El Melekh ne’eman), God faithful King” (BT Shabbat 119b).
“Come and see: This Qedushah is not like other Qedushot, which we triple. Rather this Qedushah ascends on all sides above and below, in all aspects of Faith, smashing locks and seals of iron and evil shells, so that the glory of the blessed Holy One will be exalted above all. We must recite it in the language of the Other Side [namely, Aramaic], and respond with mighty כֹּחַ (koaḥ), power: ‘Amen! May His great Name be blessed,’ so that the power of the Other Side is broken, the blessed Holy One ascends in glory and remembers His children and remembers His Name. Since the blessed Holy One is exalted in His glory by this Qedushah, it must be uttered only in the presence of ten” (Zohar 2:129b).
“Bezalel knew how to combine the letters with which God created the heavens and the earth [see Genesis 35:3, cf. BT Berakhot 55a]… and these are the twenty-eight letters [and seven words] of the verse בְּרֵאשִׁית בָּרָא אֱלֹהִים אֵת הַשָּׁמַיִם וְאֵת הָאָרֶץ In the beginning God created the heavens and the earth (Genesis 1:1) about which it is said, the power, of His deeds He told His people [כֹּחַ (koaḥ), power, is numerically equivalent to 28] (Psalms 111:6). But at the time of the exile, these twenty-eight letters departed, as it is said: And they have gone without כֹּחַ (koaḥ), strength, before the pursuer (Lamentations 1:6). Therefore, it is said in [the introduction to] Qaddish ‘And now, may the כֹּחַ (koaḥ), power, of the Lord be magnified,’ corresponding to twenty-eight other letters that form seven words, which are יְהֵא שְׁמֵהּ רַבָּא מְבָרַךְ לְעָלַם וּלְעָלְמֵי עָלְמַיָּא (yeheh shemeh rabba mevarakh le-alam ul-alemei alemaya), ‘May His great Name be blessed forever and eternity.’ Thus, the [Sage’s] statement, ‘Whoever answers May his great Name.., with all his כֹּחַ (koaḥ), might, becomes a partner with the blessed Holy One in the act of Creation and the giving of the Torah’ (BT Shabbat 119b)” (Tiqqunei ha-Zohar 1:13a [72a]).