Because God doesn’t change, certain benefits accrue to his people.
I’d like to begin with the obvious observation that an unchanging God is trustworthy, or reliable. He tells the truth. He doesn’t lie, or even change his mind. And his word comes true; he never fails in a promise or a prediction.
God is not a man, that He should lie,
Nor a son of man, that He should repent;
Has He said, and will He not do it?
Or has He spoken, and will He not make it good? (Nu 23.19).
The Glory of Israel will not lie or change His mind; for He is not a man that He should change His mind (1S 15.29).
The Lord of hosts has sworn saying, “Surely, just as I have intended so it has happened, and just as I have planned so it will stand” (Is 14.24).
“I, the Lord, have spoken; it is coming and I will act. I will not relent, and I will not pity and I will not be sorry; according to your ways and according to your deeds I will judge you,” declares the Lord God (Ezk 24.14).
Sceptics have often observed that the Scripture seems to contradict itself on this point. Sometimes it says that God doesn’t change his mind (“repent”) and sometimes it says that he does.
I won’t dispute that. That’s what the various verses say. But I note something else: three of the allegedly contradictory verses occur in the same passage, 1 Samuel 15. Specifically, in verse 11 God himself says that he has repented; then in verse 29 Samuel says that God (“the Glory of Israel”) will not change his mind; then in verse 35 the author says that God (Yahweh) repented.
Now, what are the odds that the author of Samuel was so incompetent, so inattentive, so stupid, that he made a boneheaded mistake like that, yet produced overall a book of such high historical and literary quality?
I can only conclude that he interplayed these terms intentionally—similarly to what Solomon did in Proverbs 26.4-5, placing two directly contradictory statements right next to each other, to make the reader stop and think: “When should I answer a fool? And when should I not?”
So what is the author of Samuel doing here? In what sense has a God who cannot change or lie or be surprised “changed his mind” with reference to Saul? What is the author communicating to us by this literary device?
This post isn’t about 1 Samuel 15; we can work through that application another time. My only point here is that God is not the sort of person whose thoughts, plans, and promises are unreliable. He doesn’t change; he keeps his promises, and you can trust him with your life on this earth and your life into eternity. You may not understand his purposes during the difficult times, or his reasons for choosing this tactic or that outcome, but you can be sure that he won’t say one thing and do another, or make a promise he cannot or will not keep.
Our most practical response to this truth is to make a point of hearing and remembering his promises. As you read your Bible, highlight the promises, particularly the ones that are given to God’s people in general. (When the ascended Jesus tells Saul in Acts 9.6 that someone will tell him what he’s to do, that’s a promise, all right, but not one made to us.)
Think through these promises, carefully considering how they can be fulfilled in your life, praying for God’s wisdom in discerning when the fulfillments come, and living in gratitude for those fulfillments. God’s people don’t simply rejoice at occasions of “good luck”; they recognize the personal source of those blessings, and they consciously allow their gratitude to strengthen and deepen their love for, and trust in, the Giver of all good gifts—and Keeper of all his promises.