Why was Peter's accusation of Israel valid in Acts 3?
Peter's accusation was valid because God had not yet revealed that Israel was no longer under law but under grace. Peter could only speak what God had revealed, and his remarks were in perfect accord with the Almighty. Biblical faith requires God's revelation before belief.
Les explains that Peter's language here is totally opposite of what Paul speaks of in his letters. Paul never points the finger at Jew or Gentile and says that they killed the Christ; instead Paul says He loved you and died for your sins. But Peter does not say that. Why? Because these things were still hidden in the mind of Peter, and consequently he could not go any further than what God had revealed. Les emphasizes that faith, biblical faith, equals taking God at His Word. If faith is taking God at His Word, God must say it and reveal it before we can believe it; you cannot place your faith in something He has never said. That is why Peter is in perfect accord with the Almighty God here. He is not out in left field by confining his remarks to Israel. He is not out in left field by accusing Israel of what they have done, because God has not said a word yet that they were not under law, but now they are under grace. Les then uses a verse to back this up, turning to Romans chapter 10.