Matthew 18:15-16,18:

(Jesus said) “If your sister or brother should commit some wrong against you, go and point out the error, but keep it between the two of you. If she or he listens to you, you have won a loved one back; if not, try again, but take one or two others with you, so that every case may stand on the word of two or three witnesses. . .  The truth is, whatever you declare bound on earth will be bound in heaven, and whatever you declare loosed on earth will be loosed in heaven.