Holy relics can be found in many different religions, whether Christian, pagan, Hindu, or Buddhist. A relic is defined as something directly associated with a revered saint, teacher, ancestor, or some miraculous manifestation of deity in the material world. A relic and a reliquary are two types of sacramental tools. A reliquary is a container or box for a relic, allowing it to be displayed to the public and thus transfer its powers to magical and liturgical works. There is another definition of a relic: anything that would be a miraculous manifestation of a deity in the material world. In Christianity, there are countless numbers of relics, most of them being associated with Jesus Christ.

In the early years of Christianity, it was forbidden to move and share the remains of saints and martyrs, and they were protected so that their final resting places, such as catacombs and cemeteries, remained intact. The earliest recorded Christian relics, specifically the bones and ashes of martyrs, date from the 2nd century. 200 years later, St. Ambrose and others set out to dig up the corpses and honor them. At that time, it was considered that every holy body could be dismembered and divided among the faithful to worship it. The remains of corpses sometimes came into someone else's hands as a gift, and sometimes they were stolen. At one point, the demand for holy bodies was such that bodyguards were assigned to dying saints to prevent their bodies from being dismembered after death.

The veneration of the relics of saints was so common among the faithful because they believed saints in Heaven interceded for believers on Earth. As a result, numerous healings and miracles were attributed to the relics, and many stories and myths about miracles arose from these beliefs. By word of mouth, the stories spread among the faithful, and finally, they were recorded in books.