A.T. Robertson Commentary Matthew 18:18

"Verily I say unto you, what things soever ye shall bind on earth shall be bound in heaven; and what things soever ye shall loose on earth shall be loosed in heaven." — Matthew 18:18 (ASV)

Shall be bound in heaven (εστα δεδεμενα εν ουρανω). Future passive periphrastic perfect indicative as in "shall be loosed" (εστα λελυμενα). In 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.