3:19 "Repent therefore and be converted, that your sins may be blotted out, so that times of refreshing may come from the presence of the Lord, 20 and that He may send Jesus Christ, who was preached to you before, 21 whom heaven must receive until the times of restoration of all things, which God has spoken by the mouth of all His holy prophets since the world began."
Jesus is the Lamb of God slain from the foundation of the world. The Bible repeats this truth in several places. The plan for Jesus to rescue us was laid from the beginning. This is why an animal was killed to make skins for clothing for Adam and Eve. This is why Abel and Cain were both sacrificing lambs on altars until Cain decided to offer his produce instead. The animals dying represented Jesus dying. His life "clothes" us. His death is in place of ours. He is in every way the Lamb slain from the foundation of the world. (Rev. 13:8)
To help the people better understand the Story of how Jesus would save us from our sins He gave Moses detailed instructions for the sanctuary and all the things that would happen there. Each piece of furniture represented Jesus in some way and our relationship to Him.
What does this have to do with Peter's words to the crowd that gathered after the lame man was healed? Lots actually. Notice that Peter tells them to "repent and be converted, that your sins may be blotted out..."
That is sanctuary language. The blotting out of sins refers to a specific event. Search the phrase "blotted out" or "blot out" and you will see a clear picture emerge, especially if you are familiar with the daily and yearly services of the sanctuary. Daily lambs/goats were sacrificed sins committed. Drops of blood from those animals were taken into the sanctuary, into the first room called the Holy Place. Picture the scene. The guilty person confesses his or her sins on the head of the lamb. Symbolically they are transferred. The lamb suffers the penalty for those sins. The blood becomes a visual representation for sin and it's consequences. The blood is then transferred from the courtyard where the sacrifice took place to the Holy Place. The sinner can no longer see the blood. The "sins" are removed by the priest and taken into the sanctuary. The courtyard represents the earth. This is the place where the Lamb died. Then Jesus was taken out of our sight. He is now in heaven. The Bible said from the beginning that the real sanctuary is in heaven and the one Moses had built was just a model. It was essentially a life size teaching tool.
So we have covered what happened daily at the sanctuary or temple. Have you thought about the accumulation of all those drops of blood inside the Holy Place? Then what happens?
Once a year a lamb is offered. It's called the day of atonement or Yom Kippur. The blood from that lamb is taken into the second room where the ark of the Testimony is - the Most Holy Place. The blood that has accumulated throughout the year is cleansed from the Holy Place or "blotted out".
The sanctuary has more to teach us. Our sins are currently taken away but not yet blotted out. Like my dirty clothes that I remove at the end of the day and transfer to the laundry hamper. They are removed from me but the dirt is not yet blotted out.
Jesus is the Lamb of God who takes away the sins of the whole world. Daily lambs were offered by the priests on behalf of all the people. People who didn't even come to confess. Jesus has been bearing our guilt from the beginning. The direct and immediate consequence of sin (death) has been removed from humanity but not yet blotted out. That only happens at the end. On the last day. On that day our sins either get blotted out forever (because we repented and were converted) or they are not because we refused His grace and trampled on His mercy.
It sounds complicated but really it is not. Jesus has taken our dirty laundry until we decide what we want Him to do with it. Clean it or give it back...