Matthew 18:18
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.
Cross-references
Matthew 16:19
Parallel
Matthew 16:19 gives Peter the same binding/loosing authority that Jesus here extends to all disciples — identical teaching.
John 20:23
Parallel
John 20:23 parallels binding/loosing with forgiving/retaining sins — both grant apostolic authority over forgiveness.
2 Corinthians 2:10
Parallel
2 Corinthians 2:10 demonstrates apostolic forgiveness, corresponding to the 'loosing' aspect of binding and loosing in Matthew 18:18.
Isaiah 22:22
Typology
Isaiah 22:22 describes the key of David with opening and shutting authority — a clear type of the binding and loosing power given to disciples.
John 9:34
Contrast
John 9:34 shows the Pharisees wrongly excommunicating a man — contrasting the legitimate binding authority given to the church.