Initially, this sounds like a hoity toity obscure method of saying that there is a pattern that exists in prophetic work. That God uses patterns and that the listeners of the prophets understood this. So, a key part of identifying a true prophet is investigating the pattern of the words he/she speaks. In other words, if a prophet sounded like a divine lawyer calling down God's wrath then you ought to listen. Furthermore, if it was a court then a record ought to be kept. "I see a rîb pattern in this text." Is a short way of saying a very complex concept.