What are the "keys of the kingdom" which Jesus gave Peter and the rest of the disciples? (Matt. 6:19)
Keys open and shut doors. Jesus said, "I am the door. No man comes to the Father but by me" (Jn. 14:6). There is no other name under heaven whereby men may be saved (Acts 4:12). All the scriptures testify of Jesus (Jn. 5:39). The scribes and Pharisees took away the "key of knowledge" regarding the Messiah (Lk. 11:52). They shut up heaven.
The "keys" Jesus gave to Peter were His own words, His teachings, regarding how man and women could have forgiveness for sin, freedom from condemnation, and peace through His shed blood and death on Calvary's cross. A knowledge of Jesus the promised Messiah opens heaven (Isa. 22:22).