Jamieson, Fausset and Brown on Matthew 18:18

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--Here, what had been granted but a short time before to Peter only (see on Mt 16:19) is plainly extended to all the Twelve; so that whatever it means, it means nothing peculiar to Peter, far less to his pretended successors at Rome. It has to do with admission to and rejection from the membership of the Church. But see on Joh 20:23.