One of the rules of textual criticism (dare I say one of the more important ones) is that that which best explains the manuscript evidence that we are left with is best conclusion.
That approach fits best here. As we look at the witnesses stacked up here, here's what we have:
- The Mastoretic text includes the two extra phrases, "And their sons, and the sons of their sons" (”וּבְנֵיהֶ֞ם וּבְנֵ֤י בְנֵיהֶם֙“ (Ezekiel 37:25 BHS-T)) and "And I will cause them to be many" (וְהִרְבֵּיתִ֣י)
- The LXX omits the phrases entirely (“<25> καὶ κατοικήσουσιν ἐπὶ τῆς γῆς αὐτῶν ἣν ἐγὼ δέδωκα τῷ δούλῳ μου Ἰακώβ, οὗ κατῴκησαν ἐκεῖ οἱ πατέρες αὐτῶν, καὶ κατοικήσουσιν ἐπ’ αὐτῆς αὐτοί. καὶ Δαυεὶδ ὁ δοῦλός μου ἄρχων εἰς τὸν αἰῶνα. <26> καὶ διαθήσομαι αὐτοῖς διαθήκην εἰρήνης, διαθήκη αἰωνία ἔσται μετ’ αὐτῶν· καὶ θήσω τὰ ἅγιά μου ἐν μέσῳ αὐτῶν εἰς τὸν αἰῶνα,” (Ezekiel 37:25-26 LXXS-T))
Ok, in this push-pull scenario, which is the direction to go in? Here the versions give us a little help:
- The Peshitta follows the MT very closely: "And they dwell in her—they along with their sons, and the sons of their sons, forever." (”ܘܢܬܒܘܢ ܒܗ݁ ܗ݂ܢܘܢ ܘܒ̈ܢܝܗܘܢ ܘܒܢ̈ܝ ܒ̈ܢܝܗܘܢ݂ ܠܥܠܡ“ (Ezekiel 37:25 PESHOT-T))
- The Vulgate follows the MT very closely: "and they will dwell on top of the earth for I have given to my servant, Jacob in which they will dwell—Your fathers and they will dwell on top of it/him they themselves along with their sons and the sons of their sons as far as forever." (“et habitabunt super terram quam dedi servo meo Iacob in qua habitaverunt patres vestri et habitabunt super eam ipsi et filii eorum et filii filiorum eorum usque in sempiternum” (Ezekiel 37:25 VULG-T))
- Even the Vetus Latina (which has a strong habit of following the LXX) follows the MT: "Where their fathers will dwell, and they themselves will dwell in it, along with their sons, and the sons of their sons, as far as forever." (“ubi habitaverunt patres eorum, et habitabunt in ea ipsi, et filii eorum, et filii filiorum eorum, usque in sempiternum” (Ezekiel 37:25 V-LATINA))
When one considers the fact that the the MT preserves the longer reading and all the versions (except the LXX) follow the MT, it's not difficult to conclude that this example, along with so many others, is an example where the LXX is lacking in comparison to the MT. The best explanation to describe the evidence that we have is that the LXX, being a translation of the Hebrew, messed up here.
Furthermore, only the most literalistic, formal versions of the LXX are actually useful in determining the source text due to the fact that the LXX is a translation, not the source. Tov explains it this way:
- Evidence from the translation. Only the most literal translations (like Aquila’s) represent most grammatical features of the Hebrew so
consistently and stereotypically that they can be retranslated
reliably into Hebrew. In all other translation units, that is, in the
great majority of the books of the LXX, one encounters different and
inconsistent representations of these elements, as indicated in
chapter 1.E.2; hence the techniques used by the translators provide
insufficient information for the reconstruction of many grammatical
categories. For examples relating to the LXX, see Ch. Heller,
Peshitta, Genesis (Berlin, 1927; repr. Tel Aviv, 1980), pp. xxi–xxiv. (Tov, The Text-Critical Use of the Septuagint in Biblical Research, p. 170)
Likewise, further on in the same book on LXX TC, Tov writes:
As a result of these uncertainties, it is almost impossible to
evaluate deviations in the LXX in many grammatical categories. Because
many aspects of the translation techniques cannot be analyzed
satisfactorily, no reliable variants can be reconstructed in these
areas. Moreover, when internal Greek evidence militates against the
retroversion of a given deviation in the LXX to a Hebrew variant,
Hebrew evidence complicates the situation: the reconstruction of
several types of variants which seemed improbable from the point of
view of the LXX should now be considered possible because of the
existence of such readings in Hebrew sources. (Tov, The Text-Critical Use of the Septuagint in Biblical Research, p. 171)