This account of the shepherds, unique to Luke, takes place just after the birth. It was these men themselves who told the story, deeply moved by the visit of these angels.
It is mid-October, and temperatures in the region still allow animals to be kept outdoors.
We may suppose that the angel in question is Gabriel, the bearer of news. Luke tells us that the shepherds were frightened by the multitude of angels who appeared afterwards. All these men see this scene, evidently very bright, in the dark night. Everything seems unreal!
Never before had they witnessed so tangible and impressive an apparition. Leaving their flocks unattended was unthinkable, yet verifying this heavenly message took precedence.
We can imagine Joseph and Mary's surprise at these men's arrival. Two particular events therefore marked the Messiah's birth: the shepherds' visit to the future Good Shepherd and the Magi's visit to the King of the Jews.
Mary, evidently isolated and alone after giving birth, far from her family, must have found in this visit a of encouragement and a sign that her son's birth was part of God's plan.