Matthew 18:15-17

¹⁵And 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. ¹⁶But 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. ¹⁷And 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.