Commentaries:
Robertson's Word Pictures (NT)
Shall be bound in heaven (estai dedemena en ouranw). Future passive periphrastic perfect indicative as in "shall be loosed" (estai lelumena). In Matthew 16:19 this same unusual form occurs. The binding and the loosing is there addressed to Peter, but it is here repeated for the church or for the disciples as the case may be.
Other Robertson's Word Pictures (NT) entries containing Matthew 18:18:
Matthew 16:19
John 20:23
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