Advent is divided into two parts. The first part, which runs from the beginning until December 16, focuses on the final coming of Christ. The second part, which runs from December 17 to December 24, focuses on the first coming of Christ at Bethlehem.
First reading (Isaiah 2:1-5). All of the First Readings of the Advent Sunday Masses for Year A are taken from Isaiah, the greatest of the messianic prophets.
Today’s passage contains a vision of a world at peace under God. The most compelling image here is of nations turning their weapons of war (swords and spears) into farm implements (ploughshares and sickles). But this can happen only when all nations come to the mountain of the Lord – Mount Zion in Jerusalem.
It is Israel’s task to focus attention on Yahweh, the merciful God who desires the unity of the nations. Hence, the reading ends with a call to Israel to ‘walk in the light of the Lord’. It also makes clear that the messianic blessings are meant, not just for Israel, but also for all nations.
Second reading (Romans 13:11-14). The theme is that of the Second Coming, which the first Christians believed was imminent. Paul urges the Romans to turn away from the darkness of evil, and to walk in the light of Christ. The reading thus continues the theme of walking in the light of the Lord of the First Reading.
Gospel (Matthew 24:37-44). The Gospel is a brief extract from Jesus’ discourse concerning the Parousia, the Second Coming. The emphasis is on readiness. Since the exact time of the Lord’s coming is not known, the disciples are urged to be ready to greet him at any time. The phrases ‘stay awake’ and ‘stand ready’ convey a sense of being prepared to receive the Lord.