We might reasonably expect that the first recorded preaching done by the immediate disciples of Jesus would contain the 'core' of the Gospel message. The Acts of the Apostles would therefore be a good source for determining what the first Christians believed and taught.
It's surprising then to discover that Acts says almost nothing about the death of Christ. There are, in fact, only two references in Acts to Jesus' death:
"Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Christ."
"Then know this, you and all the people of Israel: It is by the name of Jesus Christ of Nazareth, whom you crucified but whom God raised from the dead, that this man stands before you healed."
The apostles' preaching in Acts puts a greater emphasis on the exaltation of Jesus than it does on the “sacrificial death” of Jesus. Matthew’s Gospel ends with Jesus saying that “all authority in heaven and on earth has been given to me” (28:18) and we discover in Acts that the apostolic kerygma* focused more on this exaltation of Jesus than it did on His death. In fact, there doesn’t seem to be any hint at all of an atonement or sacrificial death in Acts, with the possible exception of Acts 20:28 which I discuss below. The primary message is exaltation. For example in Acts 2:36 Peter says: “Therefore let all
The only mention of "the blood of Christ" with any theological significance is in Acts 20:28 where some translations suggest it is the blood of God with which the church was bought. For example, the NIV has "Keep watch over yourselves and all the flock of which the Holy Spirit has made you overseers. Be shepherds of the church of God, which he bought with his own blood". Although some manuscripts have "church of the Lord" and some later ones have conflated this into "of God and the Lord" the evidence tends towards "of God" as the most reliable reading. However, the Nestle-Aland Greek text proposes the reading "the blood of his own" (rather than "his own blood") and a note in the NIV Study Bible adopts this reading saying this is "a term of endearment ... referring to His own Son".
This is therefore one of the only explicit statements in the earliest apostolic teachings which refers to the atoning nature of Christ’s death and it is made almost in passing without any explanation or emphasis. The church was "bought" or "obtained" or "acquired" by the blood of the Son but we get no explanation of what that means.
On the other hand, what we do get in Acts is a consistent and repeated emphasis on the exaltation of Jesus (e.g. 2:33, 36; 5:31), and this carries over into the NT letters (which I will come to later). In Acts much is made of Jesus' authority. Baptism, preaching and healing are done "in the name of Jesus" (the expression occurs twelve times in Acts, and only twice thereafter), perhaps building on the claim in 2:21 that "everyone who calls on the name of the Lord will be saved". In Acts there is "power" in the "name of Jesus". Jesus' Lordship is emphasised: for example, "God has made this Jesus, whom you crucified, both Lord and Christ" (2:36) and "Jesus Christ, who is Lord of all" (10:36). The expression "the Lord Jesus" occurs more often in Acts than in any other book.
Acts 4:33 provides a cameo of the apostolic kerygma: "With great power the apostles continued to testify to the resurrection of the Lord Jesus, and much grace was upon them all." This stands in stark contrast with those evangelists and preachers who insist that the core of the Gospel is the death of Christ as a sacrificial, atoning or substitutionary act on behalf of those He came to save. However, instead of saying "Jesus died for you" (as we might expect) the apostles clearly and consistently taught "Jesus was resurrected" and "for you" may be implicit but is not explicitly stated until we get to the later NT writings. The words "resurrection" and "raised from the dead" occur more often in Acts than in any other NT book, with the exception of the treatise on resurrection in 1 Corinthians 15.
So while we might expect the apostles to have taught that Christ died for us, that His death was necessary to enable us to be forgiven, or that our salvation is assured because of His supreme act of sacrifice, we actually find none of this in Acts. What we do find is that they taught that Jesus was raised from the dead and exalted to the highest position, at the right hand of God, and that as a result of His exaltation power has been given to those He has called. Jesus is acknowledged as the "Lord of all" and there is power in His name. If we were to look for one word to describe the effects of Jesus' death and resurrection it would be "power" or "authority" rather than "atonement", "forgiveness" or "salvation".
*kerygma is the Greek word used in the NT for "preaching" and is the technical theological term generally used to describe what Jesus or the apostles publically preached rather than what they may have believed or taught privately.