Malachi 3:6
Malachi 3:66“Because I, the LORD, do not change, you descendants of Jacob have not been destroyed.
is sometimes appealed to in JW commentary on "progressive understanding" or the "new light" doctrine — Jehovah does not change, but his people's grasp of his purposes grows clearer over time. The verse is treated as harmonising the immutability of God's character with the necessity of doctrinal revisions in the organisation. Where past Watchtower teaching conflicts with present Watchtower teaching (1874 to 1914, the faithful slave's identity, the meaning of "this generation"), is implicitly invoked: God remains the same; only our understanding has improved.
is a verse about the steadfastness of God's covenant faithfulness toward Israel — "I am Jehovah, I do not change; therefore you sons of Jacob have not been consumed." Read with the immediately preceding verses (3:1-5), the verse explains why Israel has not been destroyed despite their sin: God's unchanging character. Pair with ("God is not a man that he should lie") and ("with whom there is no variation or shadow of turning"). The verse cuts directly against the Watchtower's "new light" defence: if God does not change, and the Watchtower has reversed itself on prophet- identity, generation-meaning, organ-transplant rules, alternative-service rules, and the faithful-slave question, the inconsistency cannot be located in God. It must be located in the men doing the changing.
The NWT renders the second clause "you have not yet come to your finish" rather than the standard "you have not been consumed/destroyed." The Hebrew kalah denotes complete destruction or annihilation; the standard reading is that Israel has not been wiped out for their sins because Jehovah does not change. The NWT's "have not yet come to your finish" reframes the verse from a statement about averted divine judgement into a statement about an unfinished divine purpose — Israel is on a trajectory still in progress. The shift fits a JW progressive-revelation framing more naturally than the consensus reading does, but it loses the protective force of the original: God's immutability is the reason Israel survives, not the reason Israel still has a project to complete.