In Leviticus 19:28, the Bible says, "Ye shall not make any cuttings in your flesh for the dead, nor print any marks upon you: I am Lord." During the time that this biblical passage was written, tattoos were associated with pagan rituals and the Israelites were prohibited from that type of worship.
However, many modern Christians do not prohibit tattoos, and some have tattoos of Christian symbols. Similarly, other practices that are forbidden in the Bible, such as "Do not eat meat that has not been drained of its blood," are no longer upheld by most Christians. Many who practice the Christian faith recognize that indigenous cultures have traditionally used tattoos as a rite of passage between adolescence and adulthood and that the practice is not necessarily harmful.
The Catholic Church doesn't forbid tattoos as long as the image is not in opposition to biblical teachings and the motive behind getting the tattoo is for religious expression. Tattoos such as the crucifix or an image of Christ are favored by many Catholics. Judaism, however, forbids tattoos due to the Leviticus 19:28 passage and associates tattooing with paganism. While Orthodox Jews prohibit tattooing, many Conservative Jews do not take issue with the practice and allow people with tattoos to attend synagogue and participate in religious rituals.