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.

People's New Testament

18:18 Whatsoever ye shall bind. What was said to Peter (Mt 16:19) is addressed to all the apostles. It is spoken to all a second time (Joh 20:23). All had the keys as well as Peter. The apostles were, under the direction of the Holy Spirit, to establish the rules of the church discipline, as well as to announce the conditions of salvation by the gospel. These rules and conditions, found in Acts and the Epistles, bind and loose men. As they were to speak and write as moved by the Holy Spirit, what they announced would be ratified in heaven.

Wesley's Notes

18:18 Whatsoever ye shall bind on earth - By excommunication, pronounced in the spirit and power of Christ. Whatsoever ye shall loose - By absolution from that sentence. In the primitive Church, absolution meant no more than a discharge from Church censure. Again I say - And not only your intercession for the penitent, but all your united prayers, shall be heard. How great then is the power of joint prayer! If two of you - Suppose a man and his wife. Matt 16:19.

Jamieson-Fausset-Brown Bible Commentary

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 [1324]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 [1325]Joh 20:23.

Matthew Henry's Concise Commentary

18:15-20 If a professed Christian is wronged by another, he ought not to complain of it to others, as is often done merely upon report, but to go to the offender privately, state the matter kindly, and show him his conduct. This would generally have all the desired effect with a true Christian, and the parties would be reconciled. The principles of these rules may be practised every where, and under all circumstances, though they are too much neglected by all. But how few try the method which Christ has expressly enjoined to all his disciples! In all our proceedings we should seek direction in prayer; we cannot too highly prize the promises of God. Wherever and whenever we meet in the name of Christ, we should consider him as present in the midst of us.