Psalm 78/Notes/Lexical.v. 8.623278

v. 8 – This verse contains a unique collocation of niphal אמן with the preposition אֵת (though see the similar expression וְ֠עַתָּה אִם־יֶשְׁכֶ֨ם עֹשִׂ֜ים חֶ֧סֶד וֶֽאֱמֶ֛ת אֶת־אֲדֹנִ֖י הַגִּ֣ידוּ לִ֑י in Gen 24:49; cf. 32:11). For the intended sense, see the LXX's "with God" (μετὰ τοῦ θεοῦ). The other ancient versions likewise reflect an interpretation of God as benefactor or goal of the faithfulness, and have apparently struggled with the appearance of אֵת for such a function (hence the alternative אֶל as noted in VTH vol. 4, 373 and de-Rossi, 53). For modern translations' representation of the same result, see the DHH's "infiel a Dios," SG21's "n’était pas fidèle à Dieu," ESV "not faithful to God" (though see the KJV's "not faithful with God"). Or course, in clearer instances, such as with the verb הלך, the preposition אֵת can encode devotion (such as וַיִּתְהַלֵּ֨ךְ חֲנ֜וֹךְ אֶת־הָֽאֱלֹהִ֗ים in Gen 5:22; cf. BHRG §39.5). Indeed, van der Merwe et al. claim that while עִם and אֵת are "synonyms in the Pentateuch, in the rest of the Hebrew Bible, עִם became the default preposition to refer to all of the sense identified" for אֵת (BHRG 334, n. 7), which makes the instance in our psalm all the more remarkable.