What did Peter and the eleven tell Israel they needed to repent of?
Peter and the eleven told Israel they needed to repent of killing their Messiah, which was the worst sin they had ever committed. They appealed to the nation to recognize that they had murdered the one God had sent, and if they repented, God would yet send the king and they could have the kingdom.
Les teaches that in the transitional book of Acts, Peter and the eleven were still holding sway, appealing to the nation of Israel to repent of the worst sin they had ever committed—killing their Messiah. Peter used the words, 'You killed Him. You murdered Him.' Les explains that God would yet pick up where He left off, send the king, and they could have the kingdom. This appeal continued until Stephen, who also appealed to Israel to believe the one they killed was the Messiah, was stoned.