Saint Aelred of Rievaulx writes,

“Advent calls to mind the two comings of our Lord: the first coming of the ‘fairest of the sons of men’ and ‘the desire of all nations’, so long awaited and so fervently prayed for by all when the Son of God graciously revealed to the world his visible presence in the flesh, that is, when he came into the world to save sinners; the other that second coming to which we look forward no less than did the people of old. While we await his return our hope is sure and firm, yet we also frequently remind ourselves of the day when he who first came to us concealed in our flesh will come again revealed in the glory which belongs to him as Lord…How beautifully then at this season the Church provides that we should recite the words and recall the longing of those who lived before our Lord’s first advent!”