Or HaChaim on Leviticus 19:28/אור החיים על ויקרא י״ט:כ״ח

1 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.

2The Torah concludes the verse with the words אני השם. The reason for this is explained by Rabbi Shimon bar Yochai in Zohar volume 3, page 247. The word אני refers to G'd's throne which we are in the habit of referring to as His שכינה, His Presence. The tetragram i.e. the name י־ה־ו־ה on the other hand, is a reference to He who sits on that throne. With the expression אני השם G'd indicates that He is punctilious regarding the honour due to Him as well as the honour due to His throne. The relationship between man's body and his soul is similar to the relationship between G'd's throne and His essence. Seeing man has been created in the image of G'd, He does not want us to injure either our bodies or our souls.