Matthew 18:15-20

And if thy brother sin against thee, go, show him his fault between thee and him alone: if he hear thee, thou hast gained thy brother. But if he hear thee not, take with thee one or two more, that at the mouth of two witnesses or three every word may be established. And if he refuse to hear them, tell it unto the church: and if he refuse to hear the church also, let him be unto thee as the Gentile and the publican. 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. Again I say unto you, that if two of you shall agree on earth as touching anything that they shall ask, it shall be done for them of my Father who is in heaven. For where two or three are gathered together in my name, there am I in the midst of them.