“And you must not put a tattoo in your flesh!” (Vayikra 19:28)
It is a negative commandment that one should not write with a tattoo in our skin, as it says “And you must not put a tattoo in your flesh!”. This prohibition is to write on our flesh with a type of writing which is engraved and forever indelible. The transgression is only with a script which is engraved and written with ink or dye or other colored effects which leave a mark.
Amongst the laws of the commandment are that Chazal said that the prohibition applies to any place on the body, whether it is revealed or hidden by clothes.
Amongst the roots of the commandment are that one must distance oneself in body and eyes as much as possible from anything to do with idol-worship, and since it was a custom amongst the idol-worshippers that they would tattoo themselves with signs that they were enslaved to their idols, the Torah forbade all types of tattooing.
This commandment applies in all places and at all times, to men and to women. One who transgresses this prohibition and writes even one letter on his body with a dye which leaves a mark, receives lashes. Even if somebody else did it to him on his body, and he helped them, he receives lashes.