Parousia

In a fine, accessible essay on this topic, Dominican scripture scholar Wilfrid Harrington writes:
The Greek word parousia means “presence” or “arrival.” In the ancient Greek-speaking world, it was used to describe the ceremonial visit of a ruler or the apparition of a god.In the New Testament it is used of the appearance or coming of the glorified Christ at the close of salvation history. In dramatic fashion, it expresses faith in a final act of God that will mark the goal of human history. This act will be the establishment, in its fullness, of the kingdom of God. After New Testament times this came to be known, somewhat unhelpfully, as the Second Coming of Christ.
That's the theological definition of parousia. Hans Reinhold reminds us that the Latin adventus from which our word Advent derives is the exact Christian equivalent of parousia! Can you see how we have domesticated our notion of Advent? How we have whittled it down to a month marked by four candles in a wreath, counting off the days to December 25th? The parousia reduced to a calendar with little windows opening on pretty pictures or sweets.

If you ponder the difference here, you'll have a better take on some of the Advent scriptures (those for the First Sunday of Advent this year, for example). The startling imagery and the severe demands make more sense in light of the reality being considered: the end time and the final judgment and establishment of God's reign over creation. None of this is meant for scaring the hell out of folks. Rather the intention is to urge us to fidelity to the Lord and his word, pushing us towards the work of justice, healing and mercy, signs that the reign of God is already in our midst.

We serve the poor at Christmas not simply so that those in need will not feel left out on December 25th. Rather, we serve the poor -and are called to serve the poor every day- because such is the work, the business of the likes of us who pray:

Deliver us, Lord, from every evil
and grant us peace in our day.
In your mercy keep us free from sin
and protect us from all anxiety
as we wait in joyful hope
for the coming of our Savior, Jesus Christ.
For the kingdom, the power and the glory are yours,
now and forever.