We know Jesus is the Ultimate and Last Sacrifice, sent by the Father to fulfill the Law of Moses. On the day of Atonement, unblemished lambs were sacrificed as the offering for Israel's atonement. With these sacrifices made, the nation once again stood pure before God. Jesus was sent as the Final Sacrifice--the Sacrifice to End All Sacrifices by the shedding of blood.
Jesus' entire mission was spent leading up to the hours of his Atonement, but His birth, and particularly those to whom the message of His birth was announced, give greater insight to what he was.
We learn, from Luke, that there were shepherds abiding in the fields by night on the eve of the Saviour's birth. Though we often think "wow, the angels came even to the lowly shepherds," this is not the intent of the announcement. These were not ordinary shepherd, these were shepherds who watched over the temple's flocks (this is known because of significant internal and external evidence). These were not the average, poor, run-of-the-mill shepherds. These shepherds were well-cared for, well-off, and not what we think of when we think "shepherd."
So this may destroy the popular notion that the angels came even to humble shepherds. But there is a reason the angels came to these shepherds--a symbolic, and, therefore, much more important reason--they watched over the sheep to be sacrificed for Israel's atonement. The angels came, in essence, to say "Come, see the reason you have a job. See who will end the need for animal sacrifice." This symbolism, of shepherds leaving their flocks and coming to Jesus, foreshadows what the early saints had to do: leave behind the Law of Moses--it had been fulfilled--and come to Christ, recognizing Him as the great and last sacrifice.
