Is Jesus Quoting The Pharisees Or The Old Law In Matt 5:21?

I am amazed that some gospel preachers say Jesus is quoting the false teaching of the Pharisees in Matthew 5:21-48, when in all six cases, we can find exactly what Jesus said in the Old Testament law. A good example is verse 21 where Jesus says "Ye have heard that it was said of them of old time, Thou shalt not kill." Isn't "thou shalt not kill" an accurate quote of the ten commandments in Exod 20:13? Or is "thou shalt not kill" just a false teaching of the rabbinical fathers? Why is something this simple and clear even under dispute?Jesus goes on to say "whosoever shall kill shall be in danger of the judgment." Isn't that a fair representation of Num 35:12 and the judgment done at the cities of refuge?The truth about 21ff is - as in all six cases in Matt 5:21-48 - Jesus quotes an Old Testament verse, and then proceeds to give His stricter New Testament teaching:· don’t be angry with your brother without a cause· don’t call your brother Raca or fool