It is specifically stated in the Torah, though - as frequently the case - doesn't explain WHY....
ï¿½You shall not make gashes in your flesh for the dead, or incise any marks on yourselves: I am the Lordï¿½ (Leviticus 19:28)
Commentaries list a variety of reasons:
Tattoos were used to mark slaves.
We don't have the rights to our physical body, nor to "destroy" it.
Idol worshipers used tattoos to mark themselves.