Commentary for Leviticus 19:28

‎ ‎‎‎‎ושרט לנפש‏‎ ‎[YE SHALL NOT MAKE] ANY CUTTINGS [IN YOUR FLESH] FOR THE DEAD — This was the practice of the Amorites (a general term for heathens) to make cuttings in their flesh when someone belonging to them died.

ושרם לנפש לא תתנו בבשרכם, "And you shall not make an incision on your flesh in mourning of someone who died." The reason the Torah emphasises the word נפש is to make plain that though the incision is an injury to one's body, the reason for it is the departure of someone's נפש, someone's soul. The Torah is careful to describe this as לא תתנו בבשרכם, "do not give it on your flesh," to explain that the incision will not leave an injury on one's soul but only on one's flesh. The reason that the incision does not leave permanent damage on one's soul is that the body is considered the sheath of the soul, and man is very excited and hasty when he loses a dear relative to death (Shabbat 43). The Torah therefore continues with a different kind of bodily defacement which leaves a deeper and more permanent mark, i.e. וכתובת קעקע לא תתנו בכם, "and do not tatoo yourselves;" you will note that in this instance the Torah did not use the restrictive word בבשרכם, to show you that tatoos are considered as injuring not only the body but also the soul. The reason tatooing leaves an injury also on one's soul is that it is something which requires great care, is not performed hastily like the incision called שרט. It is only natural then that it leaves a far deeper impression on one's personality than the hastily performed incision. We are told in Baba Batra 16 that a person is not "seized" i.e. held totally responsible, for things he does at the time when he experiences deep mental anguish.

וכתבת קעקע, “nor a tatoo.” Rashi understands this to mean something engraved on one’s flesh (skin) in an indelible manner. The word would be related to תקוע, “firmly in place.” The procedure is that one “writes” with a needle beneath the skin. The area remains black forever. Our sages in Sifra Kedoshim 6,9 remark that seeing one might have thought that the mere writing on the skin would have been culpable, the Torah adds the word קעקע, to tell us that unless this writing is of such a permanent nature no penalty is incurred. At the same time, had the Torah written only the word קעקע I would have thought that the fact that an indelible mark had been made this would already have been a culpable offense, therefore the Torah had to write the words כתבת קעקע, “an indelible inscription performed with a needle-like instrument.” According to Rabbi Shimon bar Yochai, as long as the writing did not include the tetragrammaton one is not liable to the penalty for violating this commandment. He derives this rule from the ending of our verse, אני ה', meaning that unless the name of G’d was part of the inscription there is no penalty. The whole verse could be translated as: “do not inscribe My name on your flesh in an indelible manner.”