Q. Is the prohibition of tattooing oneself prohibited by the Torah only when done for avoda zarah purposes only but other decorative tattoo marks are only Rabbinical? (see next question for what difference does it make).
A. On Parashas Kedoshim, (19: 28) we read: “You shall not etch a tattoo on yourselves, I am Hashem”.
Talmud (Makos 21a) explains that the Torah attached the words “Ani Hashem” to this decree, to express that tattooing is fundamentally connected to idolatry. The Rambam, (H. Avoda Zarah 12: 11) and Sefer Hachinuch, (M 253) teach that this prohibition originated as our Torah response to avoda zarah and paganism. It was the common practice for idol worshipers to tattoo themselves, thus marking and branding themselves as slaves to their pagan gods. Our Torah demanded that we totally separate ourselves from them and their idolatrous ways.
Poskim disagree if tattooing for other purposes is a Biblical prohibition, some maintain it is. (Tosafos Gittin 20b and Aruch Laner ad loc, Rambam Tur and Shulchan Aruch don’t mention any distinction, Minchas Chinuch 253 debates the issue).
Others assert that it is only a Rabbinical injunction. (Biur Hagra Y.D. 180: 1, quoting Tosefta – Makos 3: 9. Chasam Sofer – Gittin 20b, Shoel UMeishiv 2: 1: 49, Get Poshut 124: 30, in Passhegen Haksav 9,
Horav Chaim Kanievski shlit’a argues that this is the opinion of most Rishonim.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a