From Jesus' baptism onward—when the Holy Spirit descended from heaven upon Him in the form of a dove—the image of a dove with an olive branch in its beak has been used by Christians to symbolize "God's presence with us" through both Jesus and the Holy Spirit as well as representing God's peace.
Scripture printed inside card:
"Behold, the virgin shall conceive and bear a son, and they shall call his name Immanuel" (which means, God with us). Matthew 1:23