“For I, the LORD, do not change; therefore you, O sons of Jacob, are not consumed.”
This is at once the most comforting and most terrifying promise in all of scripture, I think.
On the side of terrifying, this verse means that God’s Law is immutable. It does not change because no human — except Christ; God in human flesh — has ever or will ever keep it in its entirety. It does not change because we do not like it or happen to agree with it. God’s Law simply does not change, because the God Who made that Law does not change. Unlike human governments that change every election cycle or can be overthrown by coups or revolutions, God can never be unseated from His throne. This also means that we must all stand before precisely the same Judge. He will not be some relativistic mess of a God Who judges one group by one standard and another group by a different standard. Everyone stands before the same Judge, to be judged by the same Law. It may be that portions of the Law do not apply to some. Those who are not Levites, for example, will not be judged as Levites, but as whatever they are. Likewise for the priesthood and the regular folk and, I would hazard to guess, the Gentile. Lest anyone impugn the justice of God for applying only so much of the Law as applies to the individual, it bears note that the human justice system does precisely the same thing. I am not subject to prosecution under the laws that govern how a member of the armed forces must behave, because I am not a service person. It is just that one who does not belong to a certain governance group — like armed services members — should likewise not be subject to the laws that govern that group. The Bible sums up this premise in the phrase to whom much is given, much is required (Luke 12:48).
But this is also the most comforting verse in all of scripture. The same God Who called out to Adam, looking to restore him; the same God Who closed the door behind Noah and his family so that the water did not enter the ark; the same God Who sent judges to save Israel and bring them back into relationship with Him; the same God Who made a shepherd the king of Israel because the shepherd’s heart was like His own; the same God Who stepped down from Heaven into human history and human flesh and allowed Himself to be brutally executed for the sins of us all is the God Who waits for me to call on Him in my hours of need. He has never changed. He delivered the plan of salvation to Adam and Eve in the moments after the first human sin was committed. He expanded on that message throughout the scriptures until Jesus came on the scene and redeemed us. God is just, He has been since the beginning when He handed down judgments for wrongdoing. God is merciful, He has been since the beginning when He made the judgments endurable and promised redemption.
The same justice that has been present since the beginning is still resident in my God. The same mercy that yearns to be poured out on anyone and everyone resides within my God from the beginning of time to this day. Whether the promise that my God does not change terrifies or excites me depends on which side of His unchanging nature I find myself. If I walk in His mercy and grace, then I am daily grateful that He does not change, because it means my salvation is assured. If I walk under His judgment, then I should rightly be terrified, because His justice has never wavered and His Law is immutable. Whether I am comforted or scared by God’s unchanging nature depends not on Who He is — that has never changed — but on how I relate to Him.