Könige I 18:28 Halacha: Mishneh Torah, Prayer and the Priestly Blessing, Mishneh Torah, Foreign Worship and Customs, Sefer HaMitzvot & Sefer HaChinukh

Modulation of the voice. The voice should not be raised during the recital of the Amidah prayer nor should it be offered [silently] in thought alone. The words should be pronounced with the lips, but softly, and yet be audible to the speaker's ears. The worshiper should not permit his voice to be heard by others, unless he is sick, or is unable to concentrate his attention without reading aloud. He may not, however, do so at public worship, so that the congregants shall not be disturbed by his loud praying.

Cut-making and incision on one's flesh over the dead are identical idolatrous practices, for the idolaters, even as they made incisions on their flesh over the dead because of their sorrow so did they wound themselves in their frenzy for their dieties, as it said: "And cut themselves after their custom with knives and spears" (I. Kings, 18.28). Even this was forbidden by the Torah, for it is said: "Ye shall not cut yourselves" (Deut. 14.1), with this distinction, however, if it be over the dead there is no difference whether he made the incision by hand or by instrument he is striped, but if it be for idolatry, with an instrument he is guilty and is striped, but by hand he is not guilty.¹⁶Ibid. 21a. C.

We have been prohibited from making a gash "for a life" in our flesh like the idolaters did. This is as it is said "Lo Titgodedu." This commandment has already been duplicated when it says "a gash for a life you shall not make..." (Leviticus 19:28) ... And there it explains that one who gashes in response to a death, whether by hand or with a utensil, is liable; [one who gashes] for idolatry, with a utensil is liable but by hand is exempt [from punishment], as comes from the explanation in the Navi, "And they gashed themselves like their manner with swords." (Melachim I 18:28). Behold, they said that in the category of this [law] is the prohibition against splitting the opinions of the town in their customs. They said, "Lo Tigodedu means don't make agudot (groups)" (Sifrei Devarim 96:10), but the main meaning of the text is like we explained, don't make a gash for the dead. This is like an interpretation of the text. So too, said [the Talmud in Sanhedrin 110], "one who holds on to a legal dispute violates a negative commandment, like it says, "do not be like Korach and his congregation," which is also like an interpretation of the text indeed the body of the text is meant to scare. And according to what the Sages ...