Bede the Venerable
Catena Aurea · Lukasevangelium 2
And there were in the same country shepherds abiding in the field, keeping watch over their flock by night. And, lo, the angel of the Lord came upon them, and the glory of the Lord shone round about them: and they were sore afraid. And the angel said unto them, Fear not: for, behold, I bring you good tidings of great joy, which shall be to all people. For unto you is born this day in the city of David a Saviour, which is Christ the Lord. And this shall be a sign unto you; Ye shall find the babe wrapped in swaddling clothes, lying in a manger.
The infancy of the Saviour was impressed upon us, both by frequent heraldings of Angels and testimonies of Evangelists, that we might be the more deeply penetrated in our hearts by what has been done for us. And we may observe, that the sign given us of the newborn Saviour was, that He would be found not clothed in Tyrian purple, but wrapped in poor swaddling clothes, not laying on gilded couches, but in a manger.