Psalm 24, todays responsorial psalm, was part of a liturgy carried out at the Jerusalem temple (the mountain of the Lord). When ancient Israelites came to worship the Creator and Lord of all, they hoped to experience Gods presence in a special way and to receive a blessing from the God of Jacob. They sought Emmanuel.
The reading from Isaiah 7 is one of the most famous passages in the Hebrew Bible. It features the prophets promise of Emmanuel, a future descendant of the royal household of David. Ahaz reigned as king of Judah in the eighth century B.C. The prophet Isaiah was disappointed with Ahazs policies and looked forward to a better king. The sign he gave Ahaz was this: A virgin shall conceive, and bear a son, and shall name him Emmanuel. To Ahaz and his royal court, Emmanuel referred to the son (probably Hezekiah) who would be born to one of the kings wives. The assumption behind this prophecy was that through the future king, God would be present once more in a special way to his people Israel. The name given to him by the prophet expressed the hope that the new king would become what his name signified.
In the Letter to the Romans, Paul describes Jesus as descended from David according to the flesh. That phrase contains in it the early Christian conviction that Gods promise of Emmanuel has been marvelously fulfilled in Jesus, who through Joseph was the Son of David. What was promised to David and Ahaz has been brought to fruition in Jesus. That was a precept of early Christian faith.
The identification of Jesus as Emmanuel is made explicit in todays passage from near the beginning of Matthews Gospel. There Joseph is told in a dream that the child to be born to Mary is what Isaiah really hoped for. Throughout Matthews narrative of Jesus public ministry, we learn how he manifested Gods presence in his wise teachings and mighty deeds. In the passion narrative Jesus fulfills the Scriptures about the Suffering Servant (Isaiah 53) and the Suffering Righteous One (Psalm 22). At the very end of Matthews Gospel, the risen Jesus promises to be with us always, until the end of the age. From beginning to end Jesus is (and continues to be) Emmanuel.
Our most familiar Advent hymn begins O come, O come, Emmanuel. When we sing it, we stand beside the psalmist, Isaiah, Paul and Matthew, and we profess our faith in Jesus as Emmanuel in the flesh, as Gods presence within our common humanity. We also look forward to the fullness of Gods presence in his kingdom. The great Advent hope is expressed in the name Emmanuel.