Matthew 18:16-20

But if you are not listened to, take one or two others along with you, so that every word may be confirmed by the evidence of two or three witnesses. If the member refuses to listen to them, tell it to the church; and if the offender refuses to listen even to the church, let such a one be to you as a Gentile and a tax collector. Truly I tell you, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven. Again, truly I tell you, if two of you agree on earth about anything you ask, it will be done for you by my Father in heaven. For where two or three are gathered in my name, I am there among them.”