In the Bible a sign often means something that contains and conveys what God is doing and giving. At the same time a sign hides under what appears to be its opposite. The disclosure of a sign is by a word of God, which requires hearing and receiving faith. God's dealing with us in this way reduces us to the point at which we are nothing but receivers. The shepherds received the words of the angel and embraced the Baby in the manger as the Savior who is Christ the Lord.
Selected Sermons, page 33