Klein, the Anchor Bible volume by McCarter on 2 Samuel comments on the differences between the LXX and Masoretic Text:
3. Jacob So LXXL, OL. MT has “Israel.”
to me MT ly, for which Syr. reflects wly, “and to me,” and LXXL, OL by, “through me” (cf. v. 2). According to BHS, ly is omitted by MTMSS.
One … God The text of LXXB is seriously confused. It reads parabolēn eipon en anthropō pōs krataiōsētai (so LXXM; LXXB: krataiōsēte) phobon christou, apparently reflecting mšl ʾmr (= ʾōmār [Wellhausen]) bʾdm ʾyk tmšl yrʾt mšyḥ, “a parable. I said among mankind, ‘How will the fear of the anointed be grasped?’ “The primary corruption seems to have arisen from graphic confusion involving *ṣdq, which was mistaken for ʾk t-: ṣ and d and final k, and q and t were all easily confused, especially in the scripts of the fourth and early third centuries. As Wellhausen suggests, ʾmr is probably a mistake for ʾdm, en anthrōpō being a secondary correction towards MT. Christou might be the contribution of a Christian scribe (Wellhausen). More likely, however, it is a corruption of ischyrou, “the Mighty One,” the LXXL translation of ʾl in v. 5, under the influence of christon theou in v. 1. Note (kai) en theou at the beginning of v. 5 in LXXB, a marginal correction of phobon christou to en phobou theou that found its way into the text in the wrong place. Underlying the troubled text of LXXB, then, is a reading not substantially different from that of MT: mšl ( B)ʾdm ṣdq mšl (b)yrʾt ʾl.
One who rules The primitive text had mšl, preserved in its second occurrence below by 4QSama. It is interpreted (correctly) by MT as môšēl, “One who rules.” As noted above, LXXB understands mšl in its first occurrence as māšāl, “a parable.” LXXL (arxon) takes it as an imperative, meûšōl. “Rule!” Cross (1973:235 n. 70) prefers this, but it is inconsistent with v. 2 (“through me”) and, more importantly (since v. 2 may be secondary [see the NOTE]), it creates difficulties in the syntactic relationship between vv 3 and 4.
the fear MT yrʾt is possibly to be prefixed with b- (so MTMSS, LXXL, OL, Syr., Targ., and Vulg.); but cf. Richardson 1971:262; Cross 1973:235 n. 71.
God We should probably read ʾl, as in vv. 2 and 5, for MT ʾlhym (cf. LXXLMN; LXXA OL: “Yahweh”), as hinted by the curious reading of LXXB, christou, “(the) anointed one.” See the Textual Note on “One … God” above.