"And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven" (Matt. 16.19).
What are these keys?
a) The keys represent the authority to carry out church discipline, legislation and administration (Matt. 18.15-18).
"Moreover if thy brother shall trespass against thee, go and tell him his fault between thee and him alone: if he shall hear thee, thou hast gained thy brother. But if he will not hear [thee, then] take with thee one or two more, that in the mouth of two or three witnesses every word may be established. And if he shall neglect to hear them, tell [it] unto the church: but if he neglect to hear the church, let him be unto thee as an heathen man and a publican. Verily I say unto you, Whatsoever ye shall bind on earth shall be bound in heaven: and whatsoever ye shall loose on earth shall be loosed in heaven" (Matt. 18.15-18).
b) The keys give the authority to announce the forgiveness of sins (Jon 20.23).
"If you forgive anyone's sins, they are forgiven. If you refuse to forgive them, they are unforgiven" (John 20.23).
c) The keys are the opportunity to bring people to the Kingdom of Heaven by presenting them with the message of the salvation found in God's Word (Acts 15.7-9).
"And when there had been much disputing, Peter rose up, and said unto them, Men [and] brethren, ye know how that a good while ago God made choice among us, that the Gentiles by my mouth should hear the word of the gospel, and believe. And God, which knoweth the hearts, bare them witness, giving them the Holy Ghost, even as [he did] unto us; And put no difference between us and them, purifying their hearts by faith" (Acts 15.7-9).
The religious leaders of the day and today thought they held the keys to the Kingdom, and they tried to shut some people out. God uses us to help find others to enter into the Kingdom. To all who believe, they may enter.