Matthew 5:17 Do not think that I have come to loosen the law or the prophets. I have not come to loosen, but to fulfill.

He has not come to loosen the laws but to fulfill them

This statement is told because the Pharisees were claiming that he was teaching people to ignore the law of Moses

By fulfill, he means completely live a sinless life that no Israelite had managed, becoming the first and last to do so.

This is also why the sacrificial system was abolished too, because Jesus’ sacrifice was enough to the Lord for eternity.