[…] Advent calls to mind the two comings of our Lord.
The first is the 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 the fathers when the Son of God graciously revealed to the world his visible presence in the flesh, that is to say when he came into the world to save sinners;
The other is that second coming to which we look forward no less than did our fathers of old.
[…] To speak more precisely, however, the day we are shortly to celebrate in memory of our Lord’s birth brings him before us as a newborn child – that is to say it more expressly signifies the day and the hour when he first came into the world.
Whereas the season we keep beforehand represents him to us as the longed-for Messiah, and reminds us of the yearning that filled the hearts of those holy fathers of ours who lived before his coming.
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!
Nor do we commemorate that desire of theirs for a single day, but share it so to speak for a long period of time, because when something we greatly love and long for is deferred for a while it usually seems sweeter to us when it does arrive.
It is our duty then to follow the example and recall the longing of the holy fathers and so inflame our own souls with love and longing for Christ.
You must understand that the reason why this season was instituted was to inspire us to remember the desire of our holy fathers for our Lord’s first coming, and through their example learn to have a great longing for the day when he will come again.
We should consider how much good our Lord did us by his first coming, and how much more he will do for us by his second.
This thought will help us to have a great love for that first coming of his and a great longing for his return.
And if our conscience is not so perfect that we dare entertain such a desire, we ought at least to fear his second coming and by means of that fear to correct our faults, so that if perhaps we cannot help being afraid here and now, we shall at least be secure and fearless when he comes again.
Aelred of Rievaulx (1110 – 1167): Sermo 1 in Adventu Domini 1-6 (CCCM IIA); from the Monastic Office of Vigils, 1st Sunday in Advent, Year 1.