Jesus didn't bring a higher standard than torah. What he did was give a proper interpretation of it. In verse 17 he says he didnt come to destroy (give a wrong interpretation) of scripture but to fulfill it (give a proper interpretation). This is a hebrew idiom.
So when you read through the rest of the chapter you will notice, "You have heard". This is a key phrase for hearing oral law. In their oral writings they have extra rules and clarifications of the written word and build their fences and burdens. Jesus is coming against some of those oral explanations and giving them a better clarification.
If he said, "It is written", then that would be a whole different ballgame. Jesus can not add to or take away from the law (torah) or else he would be a sinner. What he was doing here was teaching the truth of it.
You are mistaken on a few levels. First, Jesus did not speak English and often translators have a hard time translating concepts between languages. Actually, the only way to translate concepts properly, is to explain the meaning of the words, as there are often no words that equate with the words being translated, in order to give the hearer a proper understanding of the original meaning, and that is absolutely the case here. Here is the Greek root word that was translated into the word fulfil:
G4130
πλήθω
plēthō
play'-tho, pleh'-o,
A prolonged form of a primary word πλέω pleō (which appears only as an alternate in certain tenses and in the reduplicated form of πίμπλημι pimplēmi
to “fill”
You see Jesus literally was saying he came to raise the standards of the law, and not only that the word law is derived from a Greek word that means a grazing pasture (
G3551
νόμος
nomos
nom'-os
From a primary word νέμω nemō (to parcel out, especially food or grazing to animals); law (through the idea of prescriptive usage)).
You see, the Jews understood that they had a moral obligation, before God, to live by the highest principles possible and so they didn't just look to the Torah as their rulebook, they looked at the books of the prophets, as well as using reasonable arguments to live their lives:
all these were considered law to them. It is on this bases that David ate the shew bread and was held guiltless and also the reason that the Pharisees accepted Jesus' arguments as to healing on the Sabbath day.
The word translated "destroy" actually doesn't mean destroy, but to rather it means disassemble something, or it can also be meant to free someone or something. Here are the compound Greek words which it is derived from:
G2596
κατά
kata
kat-ah'
A primary particle; (preposition)
down (in place or time)
and
G3089
λύω
luō
loo'-o
A primary verb;
to “loosen” (literally or figuratively)
And so Jesus was saying:
don't think I have come to free you from your spiritual obligations, I have come to raise the standards.
So not only does Jesus say he came to raise the standards, but then he says: "
That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.
Ye have heard that it was said by them of old time,
Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment:
But I say unto you..." Jesus was not interpreting the law, he was raising the conscious awareness of people, as raised their awareness of good and evil and thus established a new understanding to their grazing pasture. Now, Matthew 5:17 doesn't look like a verse out of context: when we see what he really meant. Jesus was saying the righteousness of the Pharisees, the Torah, and the 10 commandments, is not high enough, as raised the bar of obligation: before God and to man.