Upvote:3
I'm not a dispensationalist but you ask about Acts 3:17-26. If you want dispensationalists to comment on Acts chapter 2, that would require a separate question.
The Acts 3:17-26 statements were made by Peter to a crowd of Jews gathered in Jerusalem's temple. They had just witnessed the miracle of the man lame from his mother's womb having his feet and ankle bones strengthened, so that he could get up, walk, and leap. Peter expressed surprise to the crowd that they should marvel, because the miracle was not done in their power, but done by Jesus Christ who was now resurrected from the dead and sitting at God's right hand in heaven.
From there, God would send Christ (not the first sending, but for Christ's return - vs. 20-21). When the time comes for "the restitution of all things", heaven will no longer retain the risen Christ. Although the Jewish people needed to repent (not least for having crucified the Messiah), this assurance was given to them:
"Ye are the children of the prophets, and of the covenant which God made with our fathers, saying unto Abraham, 'And in thy seed shall all the kindreds of the earth be blessed.' Unto you first God, having raised up his Son Jesus, sent him to bless you, in turning away every one of you from his iniquities." (Acts 3:25-26 KJV)
Peter preached Christ crucified, resurrected to heavenly glory, from where he would return in the future to deal with both Jews and Gentiles. Peter was urging them to repent now, before Christ returned in glory to "rule the nations with a rod of iron" (Psalm 2).
Peter was not speaking of the need for Israel to have repented at Christ's first coming. Christ had come and gone. Peter was pointing them to their need to repent now, prior to Christ's second coming. About 3,000 Jews were saved by the end of Acts chapter 2, and by the start of chapter 4, about 5,000 men had been saved - mainly Jews. Chapter 3 (which is what you ask about) gives the gospel message Peter explained (which the prophets had previously pointed to) and all these converted Jews were added to the Church, post-Pentecost.