New Defender's Study Bible Notes
16:19 keys of the kingdom. The “keys” here are not literal keys, of course, but rather a metaphor for the message that would open the way to salvation for those hearers who would respond. A similar figurative use of a “key” is in Luke 11:52, where Jesus charged the lawyers of His day with taking away “the key of knowledge.” Peter, representing all the apostles, used these keys (i.e., the gospel message) to open the door to the Jews at Pentecost, then to the believers of Samaria, then to the Gentiles at the house of Cornelius (Acts 2:14-41; 8:14-17; 10:17-48).
16:19 shall be bound. The phrases “shall be bound” and “shall be loosed” can better be translated “shall have been bound” and “shall have been loosed.” Not only Peter but all the apostles (note John 20:21-23) would have the authority to pronounce to their listeners the binding or loosing that would have been established in heaven as an immediate result of the response of these listeners to the gospel message. Note also Matthew 18:18.