To the ancient world the obvious Christian characteristic was hope.
That hope came from two things.
(a) The Christian felt that he had been born, not of corruptible, but of incorruptible seed (1 Pet 1:23). He had something of the very seed of God in him and, therefore, had in him a life which neither time nor eternity could destroy.
(b) It came from the resurrection of Jesus Christ (1 Pet 1:3).