The Lord spoke to Ahaz and said, 'Ask the Lord your God for a sign for yourself coming either from the depths of Sheol or from the heights above.' 'No,' Ahaz answered, 'I will not put the Lord to the test.'

Then Isaiah said:
'Listen now, House of David:
are you not satisfied with trying the patience of men
without trying the patience of God, too?
The Lord himself, therefore,
Will give you a sign.
It is this: the maiden is with child
and will soon give birth to a son
whom she will call Emmanuel,
a name which means "God-is-with-us".'

1. The Lord's is the earth and its fullness
   the world and all its peoples.
   It is he who set it on the seas;
   on the waters he made it firm.
2. Who shall climb the mountain of the Lord?
   Who shall stand in his holy place?
   The man with clean hands and pure heart,
   who desires not worthless things.
3. He shall receive blessings from the Lord
   and reward from the God who saves him.
   Such are the men who seek him,
   seek the face of the God of Jacob.

From Paul, a servant of Christ Jesus who has been called to be an apostle, and specially chosen to preach the Good News that God promised a long ago through his prophets in the scriptures. This news is about the Son of God who, according to the human nature he took, was a descendant of David: it is about Jesus Christ our Lord who, in the order of the spirit, the spirit of holiness that was in him, was proclaimed Son of God in all his power through his resurrection from the dead. Through him we received grace and our apostolic mission to preach the obedience of faith to all pagan nations in honour of his name. You are one of these nations, and by his call belong to Jesus Christ To you all, then, who are God's beloved in Rome, called to be saints, may God our Father and the Lord Jesus Christ send grace and peace.

This is how Jesus Christ came to be born. His mother Mary was betrothed to Joseph but before they came to live together she was found to be with child through the Holy Spirit. Her husband Joseph, being a man of honour and wanting to spare her publicity, decided to divorce her informally. He had made up his mind to do this when the angel of the Lord appeared to him in a dream and said, 'Joseph son of David, do not be afraid to take Mary home as your wife, because she has conceived what is in her by the Holy Spirit. She will give birth to a son and you must name him Jesus, because he is the one who is to save his people from their sins.' Now all this took place to fulfil the words spoken by the Lord through the prophet:

The virgin will conceive and give birth to a son
And they will call him Emmanuel,
A name which means 'God-is-with-us'.

When Joseph woke up he did what the angel of the Lord had told him to do: he took his wife to his home.