God's Law Will Never Pass Away, Nor Will it Change

Jesus clearly states that He didn't come to destroy the law (or the prophets).

Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. 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. 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. 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.
- Matthew 5:17-20 (KJV)

The law here is a reference to God's law, the Ten Commandments.

When Jesus continues to speak (in verse 21), He remains on the topic of God's law.

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:
- Matthew 5:21 (KJV)

Jesus came here "to fulfil the law" which means "to keep it". When the law is fulfilled (kept/obeyed), it doesn't mean that the law disappears.

The phrase "Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law" means that it's easier for heaven and earth to pass away, than it is for one jot or one tittle to pass from the law. (It's not going to happen in other words)

We find the same wording in the book of Luke.

And it is easier for heaven and earth to pass, than one tittle of the law to fail.
- Luke 16:17 (KJV)

The phrase "till all be fulfilled" refers to God's dealings with man (with regards to the plan of redemption that is).

"Till heaven and earth pass," said Jesus, "one jot or one tittle shall in nowise pass from the law, till all be fulfilled." By His own obedience to the law, Christ testified to its immutable character and proved that through His grace it could be perfectly obeyed by every son and daughter of Adam. On the mount He declared that not the smallest iota should pass from the law till all things should be accomplished-all things that concern the human race, all that relates to the plan of redemption. He does not teach that the law is ever to be abrogated, but He fixes the eye upon the utmost verge of man's horizon and assures us that until this point is reached the law will retain its authority so that none may suppose it was His mission to abolish the precepts of the law. So long as heaven and earth continue, the holy principles of God's law will remain. His righteousness, "like the great mountains" (Psalm 36:6), will continue, a source of blessing, sending forth streams to refresh the earth.
- Ellen White, Thoughts From the Mount of Blessing, p. 49/50

God's law is a reflection of His perfect, never-changing character.

His law is perfect, and it will never change.