Negative commandment · Lo Ta’aseh #45 of 613
Not to make cuts in our flesh, as the worshipers of false gods do
שלא להתגודד כעובדי עבודה זרה
The verse · Devarim 14:1
בָּנִים אַתֶּם לַה׳ אֱלֹהֵיכֶם לֹא תִתְגֹּדְדוּ וְלֹא־תָשִׂימוּ קׇרְחָה בֵּין עֵינֵיכֶם לָמֵת
“You are the children of the Lord your God: you shall not gash yourselves, nor make any baldness between your eyes for the dead.”
The Rambam’s words
Not to make cuts in our flesh, as the worshipers of false gods do, as [Deuteronomy 14:1] states: "Do not cut yourselves." Gedidah is another term for cutting.
שלא להתגודד כעובדי עבודה זרה, שנאמר "לא תתגודדו" (דברים יד,א); וגדידה ושריטה אחת היא.
Why · Sefer HaChinuch #467
To not gash ourselves, like the worshipers of idolatry
“It is from the roots of the commandment [that it is] in order that we not do amongst ourselves any matter at all that is similar to the worshipers of idolatry, and like the matter that I wrote in the negative commandment of encircling the head in the Order of Kedoshim Tehiyu (Sefer HaChinukh 251).”
Who & when
“And this prohibition is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Foreign Worship and Customs of the Nations הלכות עבודה זרה וחוקות הגויים