Scope
I won't focus too much on the question of tense here - as others have noted, it tends to not map very cleanly to an English understanding of tense.
Because the core of this question is about the authorial intent of the word translated as "change" here (and its implications on religious doctrines of divine immutability), I want to focus on that aspect.
As a quick formatting note - I wanted more of answer to include links to references, but was told my the site that I can't post more than 8 links at my level of reputation. If more links are requested in the comments I can provide them there.
Answer Summary
After some study, I find it to be unlikely that the author's intent in this passage was to denote a sentiment like "I have not changed", "I do not change", or "I will not change".
Instead it is much more likely to denote a sentiment like "I have not repeated", "I do not repeat", or "I will not repeat". What exactly this means in context can be discussed further (and I will give some ideas below), but the key finding is that this passage when examined critically is not clear evidence for any doctrine of divine immutability.
Word Root and Related Words
The word in question in this passage is "שניתי"
- which is commonly accepted to be an inflected verb form of the root "שנה" (H8138, H8141)
- with the "תי-" suffix indicating a first-person singular "perfect" (but again, I won't focus on tense here) verb usage
- with final "ה" letter in the root falling away (it is a "weak" letter in this position) and in this case being replaced with the letter "י"
The main root that appears to be closely related is "שני" (H8145, H8147), which is commonly accepted to indicate the number "two", with varying inflections for cardinal and ordinal forms.
The particular form of "שני" that is used ordinally is often "שנית", which being ordinal denotes something happening a second time, or "again" - it is a repetition of something that happened prior. See Genesis 22:15, which Brown-Driver-Briggs dictionary highlights as being an example of a "similar — not identical — act, or another point in a series". So there is a notion here not only of repetition, but a sense of distinctness, in that the second occurrence is a separate and distinguishable occurrence rather than being an identical repetition.
Accepted Meanings of the Root
The three-letter root "שנה" has three main clusters of meaning given by consulting Brown-Driver-Briggs dictionary and Strong's concordance:
- indicating a calendar year (H8141)
- indicating repetition or doing something again (H8138)
- indicating change/alteration (also H8138)
The first meaning (indicating a calendar year) is fairly straightforward to reconcile with the second meaning (indicating repetition), in that a yearly cycle is a salient example of repetition. It is easy to see how the abstract idea of "repetition" could develop an everyday concrete usage relating to yearly cycles.
And the second meaning (indicating repetition) clearly fits in with the ordinal number two/"שני" (H8145, H8147), which as we showed above is used to indicate something happening "again".
It is less easy to see how the third meaning (the idea of change/alteration fits) into this concept cluster, but of course you can still come up with possible theories for this relationship - perhaps repeating something gives you the opportunity to revisit your approach and do it better the second time? Repetition is certainly an opportunity for change in that sense. Or perhaps it relates to the idea of two "similar but different" objects as expressed in the earlier mentioned Genesis 22:15 example, although that was more of an expression of two distinct things rather than expression of one thing changing over time. This last line of reasoning is more "fuzzy" and speculative, so it's perhaps best not to rely on these theories too much in our analysis.
Usage in Context
Let's take a look at the context of Malachi 3:6, the passage in question.
Malachi 1 and Malachi 2 are written in the familiar mode of an accusatory prophet, rebuking and chastising the Israelite people for their lack of fidelity, with the author emphasizing the reasons why a punishment is warranted.
And Malachi 3 then begins to describe the looming punishment.
And in Malachi 3:6, we get the following statement (formed grammatically using "כי"/"because" at the start of the first clause, and a "-ו" prefix on the first word of the dependent clause):
- Because I have/am/will not "שנה",
- thus, you all, sons of "יעקב"/"Jacob", have/will not be consumed/finished.
So it seems that the fact that God is "not 'שנה'" is something that avoids an amount of punishment that would cause the "sons of 'יעקב'/'Jacob'" to be consumed/finished. From context, it must indicate some kind of moderation, mercy, or leniency in the level of punishment that allows them to survive.
If the final verb there is in the future "tense", this seems to be a statement of reassurance ("your people will not be finished/exterminated"), and if in the past "tense", this is a kind of statement of prior leniency ("your people were not finished/exterminated by my prior judgments"). Personally, I tend to think this is more of a future-oriented passage due to the context of describing a looming punishment, but I can see how it could go either way, and as mentioned before, the "tense" of this verse is not the central point of my argument.
So which of the following interpretations (based on the three meaning clusters examined in the prior section) makes the most sense?
- Your people have/will survive because I have/do/will not change.
- Your people have/will survive because I have/do/will not change [my punishment].
- Your people have/will survive because I have/do/will not repeat.
- Your people have/will survive because I have/do/will not repeat [my punishment].
Arguably the first option (the most commonly accepted interpretation/translation) is the one that makes the least sense, but let's analyze some other usage sites as well.
Similar Usage Sites
There is at least one other verses where we can find this word "שנה" in direct relation to ideas about appropriate punishment. And given that the book of Malachi is believed to have been written very late compared to other books in the canon, it is reasonable to assume that there could be some literary references in it that refer to prior works.
Proverbs 31:4-6 says the following, with the word we're studying being translated as either "pervert" or "change":
[...] It is not for kings to drink wine, nor for princes intoxicating drink;
Lest he drink ("שתה"), and forget what has been decreed, and "pervert/change" ("שנה") the judgment of all the sons of the afflicted.
First of all, note the wordplay here that the proverb is based on - the similarity between the word "שתה" and the word "שנה", with the implication being that one leads to the other. This is the kind of thing that would make a proverb "catchy" and easy to remember.
But let's imagine for a moment that we didn't have an established tradition of translation/interpretation here and approach this usage of the word with fresh eyes.
The "calendar year" meaning doesn't fit at all - the word clearly isn't being used in that way.
The established "change" meaning does fit reasonably well here - if the original decree is forgotten, then the monarch might change their punishment without knowing it.
But the "repetition" meaning seems to fit even better - if the original decree is forgotten, then the monarch might actually repeat the punishment, punishing a person twice for the same crime, or even worse, punishing the person's sons, as the text does say "sons of the afflicted" rather than just "afflicted". Note that punishing children for the crimes of the parent would contradict the principle expressed in Ezekiel 18:20.
A just monarch would punish appropriately for a crime, but would not double or repeat their punishment.
To reinforce this interpretation, there are other occurrences of this word in the book of Proverbs that refer to repetition as well.
Proverbs 26:11:
As a dog returns to his vomit, a fool repeats ( "שונה") in his folly.
Proverbs 17:9:
One who covers a transgression seeks love, but one who repeats ("שנה") on a matter divides best friends.
Note that this latter one also hints at a kind of mercy that is actually a bit relevant for our Malachi 3:6 example: the idea that through or in the pursuit of love a transgression can be forgiven/forgotten, because repeatedly harping on an old transgression often deepens divisions rather than heals them.
Return to Malachi 3:6
Returning to Malachi, I think it's simplest to suggest that repetition is the key idea:
The punishment of the sons of Jacob will not be dealt with appropriate (and perhaps even merciful) restraint. The punishment will not repeated unnecessarily or excessively, and it will not be repeated so much that they will cease to exist, or that the relationship between them and their God will not be able to recover.
Corroboration in Jewish Tradition
I don't treat the interpretative tradition of any particular modern religious group as having a flawless accuracy with regard to authorial intent or how the text was understood by contemporary readers (ancient Israelites). I think careful discursive study with an open mind will get us closer than we'll get if we assume any group or tradition already "has it right".
That said, it's worth noting that at least one sage in the diverse Jewish tradition of interpretation is documented as corroborating my interpretation here.
See Rashi and Sotah 9a
From Rashi (where it is presented as a counterpoint to the main commentary):
Our Sages (Sotah 9a), however, explained it: לֹא שָׁנִיתִי - I did not strike a nation and repeat a blow to it; but as for you, I have kept you up after much punishment, and My arrows are ended, but you are not ended.
From Sotah 9a:
Ameimar teaches that statement of Rav Ḥinnana bar Pappa with regard to this: What is the meaning of that which is written: “For I the Lord change not; and you, sons of Jacob, are not consumed” (Malachi 3:6)? “For I the Lord change [shaniti] not” is interpreted to mean: I did not strike a nation and repeat [shaniti] striking it, as a stricken nation never recovers from the initial strike.
An Aside on Divine Immutability
I think this is a particularly interesting subject because its one that I find little support for in the biblical texts, and yet it is a strongly held doctrine by many different groups.
This is one of the verses that is said to prove the point, and yet I find the evidence not very compelling - at the very least, there are alternative interpretations worth entertaining.
Why is the doctrine of divine immutability so prevalent? I suspect it has something to do with the strong influence of Platonism/Neoplatonism on the evolution of philosophy and theology within Judaism, Christianity, and Islam over the millennia between now and then.
Divine simplicity and divine immutability are key components of Platonist thinking, and these ideas have been a recurrent theme amongst the theosophical speculative works of monotheists.
But from the evidence (or lack thereof) that I've seen, these ideas were not to be found (at least in any clearly distinguished form) in the actual religious writings of the ancient Israelites that we have access to today, and are likely an anachronistic projection backward in time by later interpreters.