Isaiah 43:12

אָנֹכִי הִגַּדְתִּי וְהוֹשַׁעְתִּי וְהִשְׁמַעְתִּי וְאֵין בָּכֶם זָר וְאַתֶּם עֵדַי נְאֻם־יְהוָה וַאֲנִי־אֵל׃

Accented:

אָנֹכִ֞י הִגַּ֤דְתִּי וְהוֹשַׁ֙עְתִּי֙ וְהִשְׁמַ֔עְתִּי וְאֵ֥ין בָּכֶ֖ם זָר֑ וְאַתֶּ֥ם עֵדַ֛י נְאֻם־יְהוָה֭ וַֽאֲנִי־אֵֽל׃

12 I have declared and I have saved and I have made it known, and there is no other among you. "You are my witnesses," declares the LORD: "I am God."

אָנֹכִי הִגַּדְתִּי וְהוֹשַׁעְתִּי וְהִשְׁמַעְתִּי I have declared and I have saved and I have made it known, These three hifil perfects are all in the first person, so on the one hand God is emphasizing that he himself is the author and performer of his plan for our salvation, but on the other hand there is also an implicit support here for the doctrine of the Trinity. The Septuagint's use of the aorist simply calls the fact of God's words to our attention; the Vulgate had retained the perfect tense (-avi / -avi / feci).

וְאֵין בָּכֶם זָר and there is no other among you. זָר means "other, another" in the sense of a foreign, unauthorized or even illegal presence. The root can even mean "stinking" with Hamlet's reference to something rotten in Denmark. The Septuagint's ἀλλότριος "foreigner" brings out the flavor of this word, as does the Vulgate's alienus. The idea here is that there is a force at work, an illegal, unauthorized god among the people, but it's there as a creation of the mind of sinful man.

וְאַתֶּם עֵדַי נְאֻם־יְהוָה וַאֲנִי־אֵל "You are my witnesses," declares the LORD: "I am God." Once again, God calls mankind onto the witness stand to declare what the heavenly declare: God is God, and there is no other God. Here the only Mp reference in the verse is that וְאַתֶּם עֵדַי "you are my witnesses" occurs twice: cf. Isaiah 44:8.

Septuagint:
12 ἀνήγγειλα καὶ ἔσωσα, ὠνείδισα καὶ οὐκ ἦν ἐν ὑμῖν ἀλλότριος˙ ὑμεῖς ἐμοὶ μάρτυρες κἀγὼ μάρτυς, λέγει κύριος ὁ θεός.

Vulgate:
12 ego adnuntiavi et salvavi auditum feci et non fuit in vobis alienus vos testes mei dicit Dominus et ego Deus

Note that older versions of Bible Works have an incorrect accent on הִגַּ֤דְתִּי.