To Romans and Greeks, castration and circumcision were linked as barbaric mutilations of the male genitalia. When the cult of Cybele was imported to Rome at the end of the 3rd century BC, its traditional eunuchism was confined to foreign priests (the "Galli)", while Roman citizens formed sodalities to perform honors in keeping with their own customs. It has been argued that among the reasons for the Apostle Paul's exhortation of the Galatians not to undergo circumcision, the practice at the time should be understood not only in the context of Jewish circumcision, but also of the ritual castration associated with Cybele, whose cult was centered in Galatia. Among Jews, circumcision was a marker of the Abrahamic covenant; diaspora Jews circumcised their male slaves and adult male converts, in addition to Jewish male infants. Although Greco-Roman writers view circumcision as an identifying characteristic of Jews, they believed the practice to have originated in Egypt, and recorded it among peoples they identified as Arab, Syrian, Phoenician, Colchian, and Ethiopian. The Neoplatonic philosopher Sallustius associates circumcision with the strange familial–sexual customs of the Massagetae who "eat their fathers" and of the Persians who "preserve their nobility by begetting children on their mothers".