Let us consider what we know about God. Holiness is one of the attributes of God. Because God is holy, He cannot lie. We can trust the immutability of God's covenant because it is impossible for God to lie. Some things God cannot do, even though He is omnipotent. God cannot lie, because God is holy. To lie, He would have to violate His holiness. God cannot violate His holiness; therefore, God cannot lie.
"Since God cannot lie," someone asks, "does that mean that He is not omnipotent?" The answer is that omnipotence is not the ability to do anything; it is the ability to do anything He wills to do. He does not will to lie. He does not will to cheat, nor to deceive. He does not will to play false with His people. God wills to be true to His children, and because He is holy, they are safe.
God is perfect in wisdom, Because our own understanding is so limited, we imagine that God could conceive a scheme to redeem men, but perhaps He cannot fulfill that plan because He had misjudged something. But that is not possible.
God knows everything that can be known. When He makes a promise, He is able to make good on that promise because of who He is. He is perfect in wisdom and knows all the details -- the end from the begninning.
If God were not omnipotent, He could not guarantee His ability to keep His covenant with me. If God were not omnipotent, I could not be sure I could be saved. I would think that I was saved, but when God reached a point where somebody was strong than He, I would be lost. Knowing that "the Lord God omnipotent reigneth" (Rev. 19:6), and knowing that omnipotence means God can do everything He wills to do, I have no doubt at all about my salvation, for I am in the arms of the omnipotent God who has sworn to save me.
Suppose God were in the habit of changing His mind. I have met men who were always starting something new and then changing their minds about it. I would see them one day, and they would be excited and could hardly eat for talking -- telling me about their new project. I would shake their hand and wish them well. When I saw them two years later and inquired about that great work they had started, they would say, "Oh, that? It didn't go through."
God is immutable. When He promises something, that promise will be kept. He has assured us that we will be blessed forever, that His mercies will be upon us forever; and that we will not perish, but will be kept by Him. God, the immutable, does not change His mind about these things -- or anything.
Human covenants sometimes fail through the mortality of the promiser. A man makes a promise with every intention of keeping it, then grabs at his chest and tumbles over. They take him off to the hospital and in a few days, he is gone. He meant all right. He was wise enough to do the thing he promised, and was kind enough to want to do it, but he did not live to do it. The covenant that keeps you and me, unlike promises made by mortal men, is made and kept by the eternal God.
God cannot fail by cessation or discontinuance. God, the eternal God, lives on -- and because He lives on, we live on as long as He lives on. Isn't this an awful, a wonderful, and an awesome thought?
We are going to live as long as God lives. We did not begin when God began, because God never began, but we did. However, going forward, as long as God, the eternal God, exists and continues to be -- as long as God can say, "I am and continue to be what I am" -- you and I will in the grace of God continue to be what we are, because we are saved by a covenant, sworn to by an oath.
Wherein God, willing more abundantly to show unto the heirs of promise the immutability of his counsel, confirmed it by an oath: That by two immutable things, in which it was impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us. (Hebrews 6:18)
Those familiar with the Old Testament know what the phrase "fled for refuge" means. Israel had six cities set apart as cities of refuge. When a man accidentally killed another man, a law in Israel said that the "avenger of blood" -- the next brother, the father or the next relative of the dead man -- could take vengeance on this fellow.
The fellow that had the ax head would take off as fast as his legs would carry him, racing to the nearest city of refuge. Sometimes he barely made it in, with his tongue hanging out, panting like a tired dog, and the would-be avenger just behind him, almost within reach of the back of his neck.
He raced in, the court trial took place, and it was decided whether or not the man was to blame. If he was not to blame, then, of course, the dead man's relative could not take vengeance -- to do so would violate the law again and now he would be the murderer. That was the city of refuge. The man of God who wrote the book of Hebrews, being a Jew, knew all about these cities.
Whether a man was guilty or not, he had a right to fly to that city of refuge. If he was not guilty, that would be proved. But even if he was guilty, he still had a right to go to that city of refuge. If he made it to that city before his pursuer got to him, then he was safe.
The man of God says that we "have fled for refuge," and I can just see myself, with the devil one hot jump behind me, racing for the cross of Jesus, racing for Calvary's holy mountain. Just as I come panting in, the doors let down behind me, and the devil runs head-on into the gate and bounces off. He does not get me, because I have found the refuge and I am safe.
[excerpts from A.W. Tozer's God's Power For Your Life: How the Holy Spirit Transforms You Through God's Word]