Bede the Venerable — as excerpted in the Catena Aurea on Luke 2:8-12

“(Home. ubi sup.) For in a mystery, those shepherds, and their flocks, signify all teachers and guides of faithful souls. The night in which they were keeping watch over their flocks, indicates the dangerous temptations from which they never cease to keep themselves, and those placed under their care. Well also at the birth of our Lord do shepherds watch over their flocks; for He was born who says, I am the good Shepherd: (John 10:11, 16.) but the time also was at hand in which the same Shepherd was to recal His scattered sheep to the pastures of life.”