Matthew 18:15-20 (NKJV)
Dealing with a Sinning Brother
15 “Moreover if your brother sins against you, go and tell him his fault between you and him alone. If he hears you, you have gained your brother. 16 But if he will not hear, take with you one or two more, that ‘by the mouth of two or three witnesses every word may be established.’ 17 And if he refuses to hear them, tell it to the church. But if he refuses even to hear the church, let him be to you like a heathen and a tax collector.
18 “Assuredly, I say to you, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.
19 “Again I say to you that if two of you agree on earth concerning anything that they ask, it will be done for them by My Father in heaven. 20 For where two or three are gathered together in My name, I am there in the midst of them.”