The following is an excerpt from the book 'The Cross of Christ' by John R. W. Stott:
It is often asserted that in the book of Acts the apostles' emphasis was on the resurrection rather than the death of Jesus, and that in any case they gave no doctrinal explanation of his death. Neither of these arguments is sustained by the evidence. I am not o course wanting to claim that the apostles' sermons express a full doctrine of the atonement as it is later found in their letters. Luke's historical sense enables him to record what they said at the time, not what they might have said if they had been preaching several years later. Yet the seeds of the developed doctrine are there. Luke weaves his story round the two apostles Peter and Paul, and supplies five sample evangelistic sermon from each, in shorter or longer summaries. Thus we have Peter's sermons on the Day of Pentecost and in the Temple precincts, brief abstracts of what he said during his two trials by the Sanhedrin, and a fairly full account of his message to the Gentile centurion Cornelius and his household. Then, when Luke is recounting the missionary exploits of his hero Paul, he contrasts his address to Jews in the synagogue at Pisidian Antioch with that to pagans in the open air at Lystra, contrasts two more in the second missionary journey, namely to Thessalonian Jews and Athenian philosophers, and summarizes his teachings to the Jewish leaders in Rome. In each sermon the approach is different. To Jews Paul spoke of the God of the covenant, the God of Abraham, Isaac and Jacob, but to the Gentiles of the God of creation, who made the heavens, the earth and the sea and everything in them. Nevertheless, there was a core to the proclamation of both apostles, which might be reconstructed as follows:
'Jesus was a man who was accredited by God through miracles and anointed by the Spirit to d good and to heal. Despite this, he was crucified through the agency of wicked men, though also by God's purpose according to the Scriptures that the Messiah must suffer. Then God reversed the human verdict on Jesus by raising him from the dead, also according to the Scriptures, and as attested by the apostolic eyewitnesses. Next God exalted him to the place of supreme honour as Lord and Saviour. He now possesses full authority both to save those who repent, believe and are baptized in his name, bestowing on them the forgiveness of sins and the gift of the Spirit, and to judge those who reject him.'
Several Important points emerged from this gospel core.
First, although the apostles attributed the death of Jesus to human wickedness, they declared that it was also due to a divine purpose. Moreover, what God had foreknown, he had foretold. So the apstoles repeatedly emphasized that the death and resurrection of Jesus happened 'according to the Scriptures.' Paul's own later summary of the gospel also stressed this: 'that Christ died for our sins according to the Scriptures,... that he was raised on the third day according to the Scriptures...' (1 Cor. 15:3-4). Only sometimes are actual biblical quotations recorded. Many more unrecorded ones must have been used, as when in the Thessalonian synagogue Paul 'reasoned with them from the Scriptures, explaining and proving that the Christ had to suffer and rise from the dead' (Acts 17:2-3). It seems likely that these were - or at least included - the Scriptures which Jesus used, and therefore the doctrine which they expressed.
Secondly, although a full-scale atonement doctrine is missing, the apostolic preaching of the cross ws not undoctrinal. Not only did they proclaim that Christ died according to the Scriptures, and so according to God's saving purpose, but they called the coss on which he died a 'tree'. Luke is careful to record this fact of both the leading apostles, Peter and Paul. Peter twice used the expression that the people 'killed him by hanging him on a tree', to the Jewish Sanhedrin and to the Gentile Cornelius. Similarly, Paul told the synagogue congregation in Pisidian Antioch that when the people and their rulers in Jerusalem 'had carried out all that was written about him, they took him down from the tree'.
Now they were under no necessity to use this language. Peter also spoke of Jesus' 'crucifixion', and Paul of his 'sufferings' and 'execution'. So why their references to the 'tree' and to his having been 'hanged' on it? The only possible explanation is to found in Deuteronomy 21:22-23, where instructions were given for the body of a man, who had been executed for a capital offence by hanging, to be buried before nightfall, 'because anyone who is hung on a tree is under God's curse'. The apostles were quite familiar with this legislation, and with its implication that Jesus died under the divine curse. Yet, instead of hushing it up, they deliberately drew people's attention to it. So evidently they were not embarrassed by it. They did not think of Jesus as in any sense deserving to be accursed by God. They must, therefore, have at least begun to understand that it was our curse which he was bearing. Certainly both apostles stated this plainly in their later letters. Paul in Galatians, probably written very soon after his visit to Pisidian Antioch, wrote that 'Christ redeemed us from the curse of the law by becoming a curse for us, for it is written: "Cursed is everyone who is hanged on a tree"' (3:13). And Peter wrote: 'He himself bore our sins in his body on the tree' (1 Pet. 2:24). If in sin-bearing or curse-bearing terms, and both linked this fact in sin-bearing or curse-bearing terms, and both linked this fact with the verses in Deuteronomy about being hanged from a tree, is it not reasonable to suppose that already in their Acts speeches, in which they called the cross a tree, they had glimpsed the same truth? In this case there is more doctrinal teachings about the cross in the early sermons of the apostles than they are often credited with.
Thirdly, we need to consider how the apostles presented the resurrection. Although they emphasized it, it would be an exaggeration to call their message and exclusively resurrection gospel. For in the nature of the case the resurrection cannot stand by itself. Since it is a resurrection from death, is significance is determined by the nature of this death. Indeed, the reason for emphasizing the resurrection maybe rather to emphasize something about the death which it cancels and conquers. This proves to be the case. At its simplest their message was: 'you killed him, God raised him, and we are the witnesses.' In other words, the resurrection was the divine reversal of the human verdict. But it was more than this. By the resurrection God 'glorified' and 'exalted' the Jesus who had died. Promoting him to the place of supreme honour at his right hand, in fulfillment of Psalms 110:1 and on account of the achievement of his death., God made the crucified and risen Jesus 'both Lord and Christ', both 'Prince and Saviour', with authority to save sinners by bestowing upon them repentance, forgiveness, and the gift of the Spirit. Moreover, this comprehensive salvation is specifically said to be due to his powerful 'Name' (the sum total of his person, death and resurrection), in which people must believe and into which they must be baptized, since there is 'no other name under heaven given to men' by which they must be saved.