"I am the Lord, I change not"
Reformed Free Publishing Association
From The Coming of Zion's Redeemer, commentary on Haggai, Zechariah, Malachi, by Ronald Hanko, pages 482-483.
[Malachi] 3:6. For I am the Lord, I change not; therefore ye sons of Jacob are not consumed.
God concludes this part of the prophecy with a reminder of his own immutability (unchangeableness). This may seem out of place at first, but most certainly it is not. It is important both for those who stand in jeopardy of God’s judgments and for those to whom he promises salvation through the coming of Christ to know that he is unchangeable.
Those who continue to live wickedly and show no fear of his judgments must know that he is unchangeable especially because his judgments do not always come immediately. When they do not see those judgments, they begin to think that God is not going to judge them at all, and they become hardened in their rebellion and disobedience.
Those to whom God promises salvation—the true sons of Jacob—must also know that he does not change, because the revelation of their salvation does not always come immediately. The believing Jews in these last days of the Old Testament had to wait another four hundred years for the fulfillment of God’s word, and we too, who have seen the beginning of that fulfillment, are still waiting for its completion. We must know that “the Lord is not slack concerning his promise, as some men count slackness” and that “the day of the Lord will come” (2 Pet. 3:9–10).
We must know his unchangeableness also as the great God of our salvation. We deserve to be consumed, for we are in ourselves no different from the ungodly among whom we live. We also are guilty of the sins mentioned in the previous verse, but we are not consumed because God is unchangeable. He is unchangeable as the God of election who has chosen his people as his own from eternity and whose eternal love for them cannot fail. He reveals his unchangeableness in the sending of the Messenger of the covenant when he does not allow the sins of his people to separate them from himself, but redeems and delivers them by his Messenger. He shows his unchangeableness in giving them his Spirit and causing the gospel to be preached to them, so that through faith the righteousness of Christ becomes theirs and they stand justified before him.
Although Israel and Judah thought that God had changed because they were not enjoying his promised blessings, it was not he but they who had changed in departing from him. Nevertheless, he would save among them the remnant according to election whom he had eternally loved and whom he would not cast away; would save them for the glory of his own name and to show that he is Jehovah, the God of the covenant, the one who does not change. That he did do, and he continues to do the same today in his unchanging faithfulness.