(a) Jesus was conceived by the Holy Spirit, and was later adopted (say in his baptism) as the Son of God. This would be contrary to the Trinitarian model used in Jesus's baptism (3:22, see comments on Matthew 3:16,17 & 28:19).
(b) The eternal Son of God was given human conception by the Holy Spirit.
Luke tells us that Jesus' supernatural work was by the Holy Spirit (3:22, 4:1,18,5:17, 11:14-22). Paul even claims that Jesus's dead body was raised by the Holy Spirit (Romans 8:11). See the discussion of - kenosis- self-emptying in Philippians 2.
A more plausible model is that Luke is concerned to establish the fact that Joseph was from the royal line of David (as he makes clear in 2:4 and in the genealogy 3:23-38). It is obvious from the many genealogies in the Old Testament that the Jewish people were concerned to establish the line of descent both of their Aaronic priesthood and the tribe of Judah. So we can imagine Luke would wonder how Jesus, having been conceived by the Holy Spirit (Luke 1:23) could be given the throne of David (Luke 1:32). From his careful investigation Luke knew that Joseph had to go to Bethlehem to be registered -dia to einai auton ex oikou kai patrias David- because he was of the house and paternity of David (2:4,5). As in Matthew's Gospel, by accepting Jesus as his son Joseph gave him the title to be the rightful heir to the throne of David. (See Matthew 1:1-18). It would have been easy for Jesus' opponents to prove that Jesus did not have the genealogical title to be the Messiah/King, but there is no record of anyone questioning this. That is why Luke can include the announcement to the shepherds that the one born in the city of David -estai panti to lao- will be for his people - Christos kurios- Messiah Lord (2:11, for the word Messiah see Matthew 1:1-18). He also notes that it had been revealed to Simeon by the Holy Spirit that he would not die -prin y an idy ton Christon kuriou- till he saw the Lord's Messiah (2:26 could this be an early copyist's error for - ton Christon kurion- the Christ who is the Old Testament Lord?)
(a) John was the last of the prophets looking forward to the coming of the Messiah, but now that the Messiah's kingdom has appeared his work is done (see Luke 16:16).
(b) John was the forerunner. Once the bearer of the good news Himself has come on the scene, John's message loses its importance.
(c) The function of prophets is to speak about Caesar's world, which includes what is wrong with the political, social, and judicial situation in each country. The Kingdom is the continuing reign of the Messiah. The principles of the Messiah's reign based on love (as set out in Luke 6:20- 38)are eternal. In that sense, a prophet however great, can never be identified with that Kingdom. Luke contrasts the dourness and ascetic life style of John the Baptist with Jesus' joyful good news (7:31-35).
Matthew describes the last supper as the meal of a Rabbi with his disciples the evening before a major feast (26:17,19). The Rabbi would rehearse the meaning of the ritual, so the disciples could explain it to their families the next day. There is no way thirteen men could celebrate a Passover meal. They would each need to celebrate the ritual (after the crucifixion) with the mother and the children each taking their part. As in the other three Gospels, Luke makes clear (Luke 23:54) that Jesus was crucified on the Day of Preparation when the Passover lambs were killed (as in Matthew 26:5, 27:62, Mark 14:2, 15:42, John 19:31, 42).
The need for each of the disciples to have their family Passover lamb sacrificed in the temple might explain why the men were absent from the cross (Luke 23:49). This would mean that Luke believed, as did Mark, Matthew, and John that Jesus died at the same time as the Passover Lambs were being sacrificed for each family in Jerusalem. We can imagine that the disciples in their own family gatherings would have begun to make the connection with the Lamb of God (see John 1:29,36, 1 Corinthians 5:7, Revelation 5:6,11,13, 7:9,10,14,17,8:1).
Here are some covenant models that we imagined Mark might have had in mind:
(a) There was a previous "blood of the covenant" that sealed a covenant made at Sinai (Exodus 24:8). Here Jesus was referring to a new covenant as in Luke 22:20, and in Paul's words "This cup is the new covenant in my blood" (1 Corinthians 11:25). In place of the system of animal sacrifice system (set out in Leviticus) Jesus was instituting a new form of worship.
(b) Paul also explained "For as often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes" (1 Corinthians 11:26). This is a common view among Protestants. The only function of the communion service is to give us a vivid reminder of the crucifixion. Luke uses a remembrance model in -touto poieite eis tyn emyn anamnysin- keep doing this in remembrance of me (Luke 22:19, as in 1 Corinthians 11:25). To this Matthew has added that the blood of the covenant, is poured out for many for the forgiveness of sins (Matthew 26:28)
(c) In addition to viewing the communion both as a remembrance (Luke 22:19), and -y kainy diathyky en to aimati mou- the new covenant in my blood (Luke 2:20), Luke gives a Kingdom interpretation "so that you may eat and drink at my table in my kingdom" (Luke 22:28-30). In this model the communion service would be symbolic of servants of the Messiah gathering as a family at his table.
(d) Is it possible that Mark, Matthew and Luke, had a composite model that included the above?
Here is one such explanation. Jesus lived and died to free all peoples of the world from the heavy burden of Jewish legal interpretations, Jewish food laws, and patriarchal attitudes to marriage and divorce. His apostles were charged to make this new covenant of the love of God known. In their presence he solemnly instituted this new covenant. And they were to remember what it cost him, and might in due course cost them. In the task of making the new covenant known, they should meet weekly on the day he would rise from the dead (see Luke 18:33) and he would come to be with them (as in John 20:19, 20:26) as they gathered in his name. An essential part of the new covenant was that all his people were freed from legalism, which meant they were forgiven freely not on the basis of Pharisaic good works but by the grace of God. The result would be that the Kingdom of the King Messiah would be made joyfully visible in every place where people gathered in his name.
That model is only a start, and it probably needs to be corrected and
made wider in its scope. The world-wide Church has already tried out many
of its essential features. And every new generation will clarify the implications
and outworking of this gathering of servants of the Kingdom.