There are four Masses for Christmas: Vigil, Midnight, Daybreak, and Daytime. I don’t have time to give the full treatment but I’ll try to at least give a few points about the scriptures assigned to each.
The Vigil Mass, to be celebrated in late afternoon or early evening of the 24th, looks forward to celebrating Jesus’ birth. In the first reading — Isaiah 62:1-5 — the prophet uses several images to illustrate God’s promise to Jerusalem, which we apply also the the Church. There will be glory, like a crown or jewels. The desolation of the exile will be undone and God will become the bridegroom of his people and will rejoice with a joy comparable only to that of a husband with his bride. We speak of the Church as the bride of Christ.
With the responsorial psalm — Ps 89:4-5, 16-17, 27, 29 with 2a as the refrain — we turn from Jerusalem to David, to whom the promise of an everlasting throne was given. In the second reading — Acts 13:16-17, 22-25 — Paul preaches about Jesus as the descendant of David in whom God’s promise of an everlasting royal house and kingdom is fulfilled. The gospel — Matthew 1:1-25 — tells us that Jesus is squarely in the Davidic line. We are also told that his birth is the work of God, as prophesied by Isaiah (the Jewish Greek version of the Old Testament, the Septuagint, Translates the nonspecific Hebrew “almah” as “parthenos,” which specifically means virgin): a virgin gives birth to the savior who is rightly called “God is with us.”
The Midnight Mass, for midnight or late evening, tells directly of Jesus’ birth. First, we apply the messianic prophecy of Isaiah 9:1-6 to Jesus. It tells of the birth of a heroic descendant of David who will liberate God’s people in an everlasting and peaceful kingdom. (This has been traditionally understood to apply to Jesus, which is why some of its phrases are used in Handel’s “Messiah.”) In the responsorial psalm — Ps 96:1-3, 11-13, with Luke 2:11 supplying the refrain — we take part in the rejoicing prophesied by Isaiah. In the second reading — Titus 2:11-14 — Paul tells us that the coming of Jesus into our world gives us the grace to live righteously as we await his return in glory. The gospel — Luke 2:1-14 — is the familiar story of Jesus birth in Bethlehem. It gives a historical context, and reminds us of Jesus’ descent from David. God sends an angel to announce his birth to shepherds. Jesus did not come in power and glory, but in humility.