Peter means the Jewish hearers were to repent of rejecting and crucifying their Messiah and come out from the guilt and attitude of the generation that did so.
In the same sermon, Peter tells 'all the house of Israel' that they crucified the One God made both Lord and Christ (Acts 2:36). When they ask what they should do, he answers, 'Repent, and be baptized every one of you' (Acts 2:37-38). To 'save yourselves from this untoward generation' is to turn from joining that generation's rejection of Jesus and prove that repentance by baptism. Les shows this was Israel's message only, not yet the Gospel Paul later preached.
Acts 2:40 — This is the exact verse being asked about; Peter's command to 'save yourselves' is his exhortation to the Jewish crowd at Pentecost to separate from the generation that rejected their Messiah.
Acts 2:40 records Peter's exhortation, 'Save yourselves from this untoward generation.' In the same sermon Peter declares to 'all the house of Israel,' 'God hath made that same Jesus, whom ye have crucified, both Lord and Christ' (Acts 2:36). The people are 'pricked in their heart' and ask, 'Men and brethren, what shall we do?' Peter answers, 'Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost' (Acts 2:37-38). In Acts 3, Peter repeats the charge to 'Ye men of Israel': 'And killed the Prince of life, whom God hath raised from the dead; whereof we are witnesses' (Acts 3:12,15). He also says, 'And now, brethren, I wot that through ignorance ye did it, as did also your rulers' (Acts 3:17). These passages together show that the 'untoward generation' was the one that rejected and crucified the Messiah, and Peter's command was to turn from that guilt.
Les Feldick stresses that Peter's Pentecost sermon is addressed to the nation of Israel—'all the house of Israel'—not to Gentiles. Peter tells them plainly, 'You killed your Messiah,' and the crowd responds, 'What shall we do?' Les notes that Peter's answer, 'Repent, and be baptized,' was the same message John the Baptist had preached to Israel. The specific sin to repent of was having rejected and crucified Christ. Saving themselves from that 'untoward generation' meant separating themselves from that guilt by believing Jesus was the Christ and proving it with baptism. Les also makes the point that this is not yet the Gospel Paul later preached. Peter does not say, 'God loved us and gave Himself for us; He died for our sins.' Instead he charges Israel, 'You killed the Prince of life.' Peter has not changed the earthly ministry message: Israel was under the Law, and along with that they were to believe who Jesus was. No Gentile is in view in these early chapters.
In Acts 2, Peter's Pentecost audience was Jewish—people gathered in Jerusalem from every nation under heaven for the Jewish feast of Pentecost. Peter tells 'all the house of Israel' that they had crucified the One God made both Lord and Christ. In Acts 3 he continues, 'Ye men of Israel,' and charges them, 'You killed the Prince of life.' This is the generation that rejected and crucified the Messiah. Les emphasizes that Peter's message was to call Israel to repent of having rejected their Messiah.
Peter's answer to the crowd's question 'What shall we do?' was 'Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins' (Acts 2:38). Les points out this was the same message John the Baptist preached to Israel, and it was now directed to Israel in response to crucifying the Messiah. Believing who Christ was—the Name—was central; they were to prove their repentance by baptism. The call to 'save yourselves from this untoward generation' was a call to come out from that generation's guilt by this act of faith and obedience.
Les says Peter's message at this point is not the Pauline gospel. Peter does not say, 'God loved us and gave Himself for us; He died for our sins.' Instead he charges Israel, 'You killed the Prince of life' (Acts 3:15). Peter has not changed the earthly ministry message that Israel was to keep the Law and believe that Jesus was the Christ. Paul's later message to the Gentiles is not yet in view; Peter's early addresses are Jew-only.
Believing the Name
Les shows that during Christ's earthly ministry Israel was to keep the Law and also believe who Jesus was—that He was the Christ. This gives context to what Peter is still asking of Israel after Pentecost.
Israel's Response
Les sets up the moment: Peter had accused these Jews of killing and crucifying their Messiah, and they responded, 'Men and brethren, what shall we do?'
Repentance for Rejecting Messiah
Les explains that Peter's message to Israel was now to repent of having rejected their Messiah, and they were to prove that repentance with baptism.
Same Message as John
Les points out that 'repent and be baptized' was the same message John the Baptist preached to Israel, and it was the requirement for every Jew to accept Christ as Messiah.
No Gentiles in View
Les shows that Peter's message of repentance and baptism was directed to the nation of Israel; in Acts 3 Peter says 'Ye men of Israel,' with no mention of Gentiles.
You Killed Your Messiah
Les summarizes Peter's bold charge to the Pentecost crowd: 'You killed your Messiah'—which is what makes that generation 'untoward' and in need of being saved from.
You Killed the Prince of Life
Les contrasts Peter's accusation—'you killed the Prince of life'—with the later Pauline gospel message and stresses that this is a Jew-only message at this point.
Israel Must Believe First
Les explains that Peter was still hoping Israel would wake up to the fact that the One they killed was the promised Messiah; he would not have addressed Gentiles as brethren yet.
Acts 2:36: Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ.
This is the accusation that defines the 'untoward generation'—they had crucified the Messiah.
Acts 2:37: Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?
The convicted crowd asks what they must do, prompting Peter's direct answer.
Acts 2:38: Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
Peter tells them to repent and be baptized—the positive response to being saved from that generation.
Acts 2:40: And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation.
This is the verse in question; Peter urges them to save themselves from that generation.
Acts 3:15: And killed the Prince of life, whom God hath raised from the dead; whereof we are witnesses.
Peter restates the charge against Israel: they killed the Prince of life.
Acts 3:17: And now, brethren, I wot that through ignorance ye did it, as did also your rulers.
Peter acknowledges the people acted through ignorance, a factor Les notes was a loophole under the Law of Israel.
No. Les shows Peter's call was repentance and baptism in response to Israel's rejection of their Messiah. It was not a works-based message, but it was also not the Pauline gospel of believing in Christ's death as the basis of salvation. It was the same message John the Baptist preached to Israel.
No. Peter speaks to 'the whole house of Israel' and 'Ye men of Israel.' Les stresses that no Gentile is in view at Pentecost or in Acts 3. Peter's early messages are Jew-only.
No. In Peter's sermon, he says 'You killed the Prince of life'; he does not preach that Christ died for our sins as the basis of salvation. Les shows that is a later, distinct message that Paul would proclaim.
Watch the Teaching: Why Acts 2 Is NOT the Birth of the Church — Explained