Luke 2:20 The shepherds returned, glorifying and praising God for all the things they had heard and seen, which were just as they had been told.
When the shepherds had learned of the good news of Christ’s birth and had seen the baby in the manger as predicted, they went back to their fields…
But they where not quiet about what they had seen, they broadcast the fact giving glory to God and their Messiah who they had worship in the stable.
They repeated what they had heard, not just from the angel, but also what they had heard from Joseph and Mary; after all, they had seen it with their own eyes.