You fear the Lord of the angels, but love the little Child. You fear the Lord of majesty, but love the babe wrapped in swaddling clothes. You fear Him reigning in heaven, but love Him lying in the manger. But what sign did the shepherds receive? You will find a baby wrapped in swaddling clothes and lying in a manger. This sign meant that he is the Savior, that he is the Christ, that he is the Lord.
But is there anything great about being wrapped swaddling clothes and lying in a stable? Are other children not wrapped in swaddling clothes? What does this sign mean then? It means a great deal if only we understand it. We do understand it if we do not merely hear these tidings but also have in our hearts the light which appeared with the angels. He appeared with light when these tidings were first proclaimed to make us realize that it is only those who have the spiritual light in their minds who truly hear.
Aelred of Rievaulx, The Liturgical Sermons, Sermon Three: For the Nativity of the Lord, v 37-38 (CF 58, p. 104)