You mean scripture where Christ says he came to fulfill the law? Are you saying you are not aware where in the Gospels Christ says this?
Fulfill means do, accomplish, make happen.
Have Heaven and earth passed? Has all been fulfilled? No, Jesus has not come and Heaven and Earth have not passed.
Then not one jot or tittle has passed from the Law.
What Law?
The Ten Commandments and the moral aspect of the Law.
How do we know?
Because Jesus starts to quote some of them through out the rest of the sermon.
Matt 5:17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
Matt 5:18 For verily I say unto you,
Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
Matt 5:19 Whosoever
therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
Matt 5:20 For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.
Matt 5:21 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:
Matt 5:22 But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.
Matt 5:23 Therefore if thou bring thy gift to the altar, and there rememberest that thy brother hath ought against thee;
Matt 5:24 Leave there thy gift before the altar, and go thy way; first be reconciled to thy brother, and then come and offer thy gift.
Matt 5:25 Agree with thine adversary quickly, whiles thou art in the way with him; lest at any time the adversary deliver thee to the judge, and the judge deliver thee to the officer, and thou be cast into prison.
Matt 5:26 Verily I say unto thee, Thou shalt by no means come out thence, till thou hast paid the uttermost farthing.