As noted, many early Christians spoke and read Greek, thus they relied on the Septuagint for most of their understanding of the Old Testament. The New Testament writers also relied heavily on the Septuagint in that the majority of the quotes cited in the New Testament are quoted directly from the Septuagint. Greek Church Fathers also quoted from the Septuagint. The theology of the early church, as explained by the Fathers of the first several centuries, is based on the wording of the Septuagint.
The apostolic fathers believed that salvation was based on repentance and not solely on the ground of the death of Jesus on the cross. Robert Kraft has stated: “There is no indication in the Didache that an initial repentance connected with the idea of personal sinfulness for which Jesus' death atones was considered basic to the Christian life.”
In the Septuagint, the form of righteousness that will provide a ransom for sins is almsgiving, the financial outpouring of compassion on the poor. The Greek translation of Daniel, Proverbs, Tobit and Sirach explicitly claim that almsgiving has the power to purge sin, to atone for and redeem iniquities. The theology of the early Church provided redemptive almsgiving as the basis of atonement.
For Luke, Jesus' mission of preaching the good news of the kingdom does not imply that Israel is supplanted. Consistently, the activity of preaching, healing and of calling disciples is set within the context of the Temple and synagogue. The Lucan Jesus accepts the form and fact of these institutions including the animal sacrificial system, Temple worship, the need for repentance and redemptive almsgiving.
The synoptic gospels all note that John Baptist came preaching calling to the crowd that they should repent for the kingdom of God is approaching. John baptized with water unto repentance. Although the word, “repent” makes a few more appearances in Matthew and Mark after the initial pericopes with John the Baptist, “repentance” disappears.
The New Testament does not explain what “repent” and “repentance” means suggesting that these passages were written for a Jewish audience. Since it is so much easier to seek forgiveness from God than from your neighbor, it is understandable that the requirements of repentance were relaxed for Gentiles by Matthew and Mark.
Luke stresses more than the others the need for repentance. All three Synoptics have this saying of Jesus: “I did not come to call righteous people but sinners”; only Luke adds “to repentance.” Luke will not let us escape the demand for repentance. Luke tells us that Jesus uses the repentance of Ninevah as a rebuke to the present unrepentant generation and that he even uses the failure of Tyre and Sidon for the same purpose. Jesus invited his audience to reflect on Pilate’s killing of the Galileans and on the death of those on whom the tower in Siloam fell. He said, “Unless you repent you will all perish likewise.”
When there is repentance, there is joy in heaven. The Lucan Jesus in successive parables repeats this statement. Repentance means an end to sinning. When this happens there is joy beyond this earth. Matthew has a parable about a shepherd looking for a lost sheep and his joy in finding it. In Luke’s version of the story, Jesus says “there will be more joy in heaven over one sinner who repents than over ninety nine righteous persons who need no repentance.” Absolute eschatological reversal results from repentance.
The Septuagint version of the Servant Poems is of interest because it represents one of the earliest interpretations of the Hebrew text. The Septuagint version of the 4th Servant Poem was cited by New Testament writers including Luke in Acts 8:32-33 and was read and commented on as Sacred Scripture by the early Church Fathers. For instance, Clement of Rome (1 Clement) makes one of his longest quotes from Scripture from Isaiah 53:1-12 LXX in 95 CE. For 1 Clement (16:1-14), Isaiah 53 is a passage which teaches humility in the community exemplified by the humility of Christ.
The LXX in Isa. 53:9a, 10-11b rewrites the outcome of the servant’s suffering excising his sacrificial death and any notion of vicarious atonement. “The 'punch line' for the Christian gospel--the description of the Servant's divinely intended sacrificial death, his justification of the many, and allusions to his resurrection--occurs only in the Hebrew texts.”
Paul trained in the Hebrew MT was certainly aware of the differences between the MT and LXX. One synoptic writer used the LXX and consistent there with has no theology of the cross. Luke has no equivalent of the ransom saying (Mk 1:45; Matt 20:28) nor of Matthew’s connection of Jesus’ covenant blood with the remission of sins (Matt 26:28). The other two synoptic scribes also used the LXX but influenced by Paul included the theology of the cross to replace the redemptive almsgiving they found in Luke. Mark does recognize, having traveled with Paul, that the theology of Luke is pre-Pauline and very Jewish. This theology of the cross is the gospel message and appropriately there are 11 instances of EUAGGELION in the synoptics (4 in Matthew, 7 in Mark, 0 in Luke).
The first followers of Jesus worshipped in the Temple every day. Paul offered an animal sacrifice in the Temple. There was no need to develop a theology of the cross for people who believed in the animal sacrificial system and the High Priest, who was the captain of their salvation, and for people who had not been excluded from the Temple. Perhaps the dispute narrated in Acts was not simply about food for widows but exclusion from the Temple and exclusion from the redistribution of food donated to the Temple.
These people would have a need to develop a new theology and according to Heitmuller, it developed in pre-Pauline Hellenistic Christianity. Thus Walter Schmithals, The Theology of the First Christians, can state: "Wilckens (1982, 155) like Raisanen (1986, 21-22, 242ff) limits the criticism of the Torah by the ‘Hellenists,’ who were persecuted by Paul, to a criticism of the temple cult, which was put forth because Jesus' atoning sacrifice made the temple cult superfluous.” Esler states: “It is indeed, very difficult to imagine how a theology of atoning death of Jesus, already present in Paul and Mark and, indeed, in pre-Pauline and pre-Marcan traditions, could have arisen among Jews who preserved close links with the sacrificial cult.” As long as the Temple stood, the High Priest was in office, the Day of Atonement was being observed and Judaism recognized the followers of Jesus as Jews, including many priests who were obedient to the faith, there was no need or reason for Luke to proclaim a theology of the cross and in fact, Luke has no theology of the cross.
Wilheim Heitmuller concluded that Luke represents the earliest traditions in that Luke has no theology of the cross, no atonement theology. Considerable evidence has been assembled by Birger Gerhardsson that Luke is very much dependent upon Palestinian tradition. Adolf Schatter has shown that the text's character together with other indicators point to the author's provenance from the Jewish church.
A number of scholars would have us believe that the Ethiopian Eunuch made a comment in response to a question from Philip while reading from Isaiah 53:7-8 LXX. Philip then responded providing an explanation based upon the MT using language about how Jesus died on the cross for our sins that could not be derived from any version of the LXX.
The Eunuch initially found comfort in Isaiah because 56:4-5 provided that believing eunuchs are included as members of the covenant. How then would he have felt if he did not find the explanation provided by Philip in his copy of the LXX? In fact, neither the Ethiopian Eunuch nor any Greek speaking person would be able to find the explanation provided by Philip in his copy of the LXX which was the adopted scripture of the community of the followers of Jesus.
What then are we to make of this theological discontinuity? It is no wonder that Gnostic groups developed claiming to possess secret knowledge imparted to them by their faith explaining their scripture.
True Repentance is hard to perform. Consequently, Matthew and Mark had to rewrite Luke to make it palatable by reducing its significance. Matthew and Mark also introduced the theology of the cross missing in Luke. These two changes have a negative correlation. Furthermore, both Matthew and Mark misunderstood the Sign of Jonah and the finger of God, reduced the role of Satan and both Matthew and Mark rewrote Luke to correct “errors.” Theology does change to meet social need.
A work in progress.
Gospel of Luke
 David A. Sapp, “The LXX, 1QIsa, and MT Versions of Isaiah 53 and the Christian Doctrine of Atonement.”
 I accept the conclusions of Bart Ehrman that verses Luke 22:19b-20 were added by 2nd century scribes.
 Esler, Community and Gospel in Luke-Acts: the social and political motivations of Lucan theology (1987), 158.