After looking at 1 Samuel 15 and seeing how the LXX translated the verbs with God as the subject I thought it would be good to see how Num. 23:19 handled a similar subject to 1 Sam. 15:29. Below is an oracle of Balaam which he declared to Balak concerning the reliability of God to bring about what he has spoken about Israel.
Num. 23:19 οὐχ ὡς ἄνθρωπος ὁ θεὸς διαρτηθῆναι οὐδὲ ὡς υἱὸς ἀνθρώπου ἀπειληθῆναι αὐτὸς εἴπας οὐχὶ ποιήσει λαλήσει καὶ οὐχὶ ἐμμενεῖ
Not like a man is God to be deceived nor like a son of man to be threatened, when he has said will he not do? When he speaks will it not remain?
εἴπας and λαλήσει
The future verb ποιήσει requires that the aorist participle εἴπας be translated in a temporal sense, ‘when he says(said)…’ in the form of a question (cf. NETS). The next clause starts with a future λαλήσει (‘when he says’) and continues with a future ἐμμενεῖ (‘remain’). Thus the tenses between these two clauses seems confused, ‘when he has said, will he not do? When he speaks will it not remain?’ The MT has two past tense verbs: ‘Has he said and will he not do or has he spoken and will he not bring it about?’ (Could the LXX translators have read the qal perf אָמַר as a qal part. אֹמֵר?)
LXX vs. MT
In both of the comparative clauses in the first half of the verse the translator has added the particle ὡς (‘like, just as’). This seems to be a clear anti-anthropomorphical addition so that the translator “has avoided any notion of God being human in any way” (Wevers, 394). It’s not that he is not a man, it is that he is not even like a man!
διαρτηθῆναι vs. ויכזב
The LXX has translated the piel imperfect of כזב,’to lie’ (BDB) as a passive infinitive from διαρταω, ‘to deceive, mislead’ (LEH). Thus, instead of God being described as one who will not lie (so MT) he is described as one who cannot be lied to (so LXX).
ἀπειληθῆναι vs. ויתנחם
The use of the Hitpael of נחם (‘to repent, show compassion on’) is probably the only use of this stem in the Hebrew BIble that demands the translation ‘to repent, change mind’ (though Deut. 32:36 is a possible exception). The LXX has changed this to claim that God cannot be threatened. Wevers thinks that this services as an intensifying interpretation of the MT, “Not only does God not repent, he cannot be coerced in any way” (Wevers, 394). Not surprisingly Symachus has gone with the more literal rendition ινα μετανοηση (‘so that he [may not] repent’). Interestingly, however, though the LXX’s rendition does speak to God’s reliability (i.e., he cannot be coerced) it allows for what the MT does not, God changing his mind in any way. I wonder then, if this is not so much intensive (so Wevers) as harmonistic to the many passages where we here of God changing his mind or repenting (Gen. 6:6; and Exod. 32:14 come most readily to mind, though the LXX has an interesting rendition in both of those passages).
The LXX has done interesting interpretive work in rendering this theologically dense passage. It has added the comparative ὡς (‘like, just as’) so that God is not even ‘like’ humankind. It has also translated both verbs as passives so that it is not that God does not lie (would it be theologically wrong to even consider God as lying?) but that he cannot be deceived. And it is not that God does not change his mind, but that he cannot be coerced. If I am thinking in terms of a transcendent or immanent portrayal of God, I see the first two changes/addition as portraying a more transcendent God. He is more removed by the addition of ὡς (‘like, just as’) and having God the subject of the verb lying (even in the negative) is avoided by making it passive. However, the last change, from God not repenting to God not being coerced, seems to me to be harmonistic to other passages regarding God changing his mind. It is not that God is not free to change his mind, it is that us mere humans cannot bring it about.
J. Lust, E. Eynikel and E. Houspie, A Greek-English Lexicon of the Septuagint, 2 Vols. (Stuttgart, Germany: Deutsche Bibelgesellschaft, 1992, 1996); John W. Wevers, Notes on the Greek Text of Numbers (Atlanta, GA: Scholars Press, 1998).