http://www.ccel.org/ccel/mcgarvey/gospels.vii.ii.html
Or have ye not read in the law,
But I say unto you…
Jesus explicitly presents his own authority as being on a par with the OT law. His “but I say unto you” is intended to correct the pharisees’ misunderstanding and misapplication of the OT law regarding work. He does not refer to other authorities but to himself.