The imagery of a lamb in the New Testament is built upon how lambs were used in the Old Testament. Lambs were among the animals that were sacrificed by the ancient Israelites as an atonement for humanity's sins. Sacrificial lambs took the place of a human sinner, absorbing the cost of sin, which is death. The New Testament teaches that as animals took the place of people in the sacrificial system, so Jesus takes the place of sinners when he dies for their sins upon the cross.
The symbolism of the lamb, used by Christians today can have different meanings:
In general, the lamb represents Jesus, "the Lamb of God" (Agnus Dei).
Standing with a banner, the lamb represents the risen Christ triumphant over death.
Standing with a cross and a gash in its side, it symbolizes the passion of Christ.
Seated on a throne or a book, the lamb represents the judgment of Christ.
Because the lamb is humble, gentle, and innocent, lambs are sometimes engraved on the tombstones of children.