1 Peter 5:13

13The Church which is in Babylon, elect together with you, greets you, as does my son, Mark.
5:13The word Babylon is here used to refer to Rome. Mark is the writer of the Gospel of Mark, who himself was a student of Peter. Mark is referred to as Peter’s son, because Mark was about the age of a son to Peter and because the relationship was like that of father and son in the Faith.(Conte)
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