God’s law (Ten Commandments) is unchangeable, unalterable, infinite, and eternal.
“For ever, O LORD, thy word is settled in heaven.” Psa 119:89. “The works of his hands are verity and judgment; All his commandments are sure. They stand fast for ever and ever, And are done in truth and uprightness.” Psa 111:7-8.
Christ could not destroy (abolish, cancel, revoke, etc.) His law, because it is a reflection of Himself; His character. If He could have done away with the law then there would have been no need for Him to die, remove Adam and Eve from the garden of Eden, have sacrifices, etc. He said “My covenant will I not break, nor alter the thing that is gone out of my lips.” Psa 89:34
Christ said He came to fulfil the law meaning to carry out, to uphold, to give an example, as was said “For even hereunto were ye called: because Christ also suffered for us, leaving us an example, that ye should follow his steps:” 1 Peter 2:21.
He says “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 5:19