The will that Rav Naftali Katz, author of Semichas Chachamim, authored was printed in dozens of editions. Part of it turns to his sons and instructs them on their ways in life. There, Rav Naftali cites the Arizal and lists twenty-one things that sanctify a person, and when a person is careful about them, he fulfills the mitzvah of “Vehiskadashtem veheyisem kedoshim” (Vayikra 21:7).
Among the things, Rav Naftali lists is answering amen with kavanah. He writes (letter 21 ibid):
“The intention of amen means that he should answer amen with all his strength, literally, because the voice arouses kavanah, as we see in the tefillos of Rosh Hashanah and Yom Kippur that one is allowed to daven aloud to arouse one’s kavanah...And he should have in mind when answering: ‘Kel Melech Ne’eman’ (see Shabbos 119b)... ‘Kel’ is chessed, as it says (Tehillim 52:3): ‘Chessed Kel kol hayom.’ ‘Melech’ is din, as it says (Mishlei 16:10): ‘Melech bamishpat ya’amid eretz’...’Ne’eman’ is rachamim...as its says ‘Ani Hashem’ – ne’eman to pay good reward and ‘Ani Hashem’ ne’eman to punish (see Rashi Shemos 6:2). He also should have in mind: Shem Havay”ah and Adnus, which combined equal the numerical value of amen.
And when he does all this, he will be called a kadosh, as it says (Vayikra 20:7): ‘Vehiskadashtem veheyisem kedoshim ki Ani Hashem Elokeichem.’ And it is explained (Brachos 53b): ‘Vehiskadashtem...Ani Hashem Elokeichem is a brachah [Birchas Hamazon], and if the mevarech is called kadosh – then how much more so is the oneh amen called kadosh because gadol ha’oneh amen yoser mei’hamevarech.’ (Brachos ibid).
