Matthew 16:19 has Jesus saying, "I will give you the keys of the kingdom of heaven; and whatever you bind on earth shall have been bound in heaven, and whatever you loose on earth shall have been loosed in heaven.” What does that mean?
If we go back to the Greek, which was one of the lingua franca at the time, especially in the Asia Minor/Palestine area, the word 'keys' is from the word 'kleis'. It is in the New Testament six times. It means authority. What are these keys? They are not actual literal keys like someone gives to others to let themselves into a place. In each reference it is symbolic of holding some kind of power over something else. When Jesus says that we have the keys of the kingdom it means that we have been given authority on this earth. We will be heard from heaven. We will be given authority from heaven. Why? We are kings! See Lesson 79 This is the background, the big question is where did the keys come from? Keep in mind some of this is just an opinion because the Old Testament doesn't mention keys although other terms are used in there that are connected. Such as "dominion", "rule", and "subdue" have clearly the same concepts. We are to rule. But 2 Corinthians 4:4, Ephesians 2:2, and John 12:31 says that satan rules the earth. Now how could both be right? Somewhere along the line satan gained the keys to this world. And that day came the day that Adam fell. We bowed down to satan and he became the ruler of the world.
We were supposed to rule this world and live forever; one with God (Elohim) the Creator but Adam disobeyed God and basically gave satan the keys to the earth. We handed dominion over to him. We died that day. Our souls and bodies were now able to die. Our bodies now decayed. Our souls now went to the grave (Sheol) waiting for judgement. There are two parts to Sheol; Hades and Paradise. When Jesus's body died, His soul went to Paradise and released all the souls. The souls went back to their bodies, Matthew 27:52-53. These resurrected saints gained life again and were taken to heaven when Jesus ascended. We lost the keys and the only way we could get it back is if God Himself came and took them back. While He was in Paradise he took back the keys for us. Revelation 1:17-18 says, "When I saw Him, I fell at His feet like a dead man. And He placed His right hand on me, saying, 'Do not be afraid; I am the first and the last,and the living One; and I was dead, and behold, I am alive forevermore, and I have the keys of death and of Hades.'"
We now have been given the keys to the kingdom. Peter passed on those keys because the church was founded on him. We are the church. We have those keys. Jesus holds the keys to death and Hades. Satan has no more dominion over us, unless we don't use those keys. Death will not stop us.