Third Maccabees book opens rather abruptly with the news of Philopater IVs victory over Antiochus III at the battle of Raphia (1:1-5). Ptolemy IV Philopater (221-203) was a weak and indecisive king, initially not defending his territory until the Antiochus III was in Egypt. When he did act, he was relentless. When the two armies met at Raphia in 217 B.C. Antiochus III had 62,000 men, 6000 cavalry and 102 elephants; Ptolemy had a nearly equal force of 70,000 men, 5000 cavalry, and 73 elephants (Polybuis, Histories, 5.79). Antiochus lost 17,000 men in this battle and Ptolemy annexed Palestine.

The Leiden First Maccabees manuscript (Codex Per F 17)
The peace Ptolemy made with Antiochus III turned out to be a mistake since Antiochus would recover and shift the balance of power in favor of the Seleucid dynasty. Ptolemy IV escaped an assassination plot when a Jew named Dositheos replaced the king with an “insignificant man” who was killed instead of the king.
What is interesting is the description of Dositheos as a Jewish person who later “changed his religion and apostatized from the ancestral traditions” (μεταβαλὼν τὰ νόμιμα καὶ τῶν πατρίων δογμάτων). The noun νόμιμος refers to a statute or law (LXX Lev 3:17, for example) rather than the Torah itself. It is the word used 1 Maccabees when the Seleucids suppress traditional Jewish practices (1:14, 42, 44), similar to 3 Maccabees 3:2. These are ancestral traditions since they come from the “decrees of the fathers.”
Dositheos alienates himself from these ancestral traditions using ἀπαλλοτριόω. This word has the sense of being an outsider or a stranger. It is used in LXX Hosea 9:10 to describe the Israelites who shamefully worshiped the gods of Baal-peor and became detestable like the thing they loved.” This may be a significant intertext since the response to the apostasy at Baal-peor was the zealous action of Phineas, a model for Matthias at the beginning of the Maccabean revolt (1 Macc 2:26, 54). The verb also appears in LXX Jeremiah 19:4 with reference to profaning the sanctuary. In LXX Ezekiel 14:5-7 the house of Israel has become estranged from God because they worshiped idols.
Although it is unlikely Paul has this particular text in mind, he does use the same sort of language to describe Gentiles in Ephesians. Gentiles were alienated from God (4:18) and the “commonwealth of Israel” (2:12), separated by the law of commandments (τὸν νόμον τῶν ἐντολῶν) and decrees (ἐν δόγμασιν). As a Second Temple period Jewish writer, Paul describes the Gentiles in the same way the writer of 3 Maccabees describes Dositheos.
By giving up ancestral practices which set him apart as a Jew, Dositheos has made himself a stranger and an outsider both to Israel and to God. His estrangement is demonstrated by preserving the life of Philopater, who will defile the Temple and outlaw ancestral traditions (3 Macc 3:2).
The warning to the reader in this opening paragraph that to apostatize from the ancestral traditions has far reaching implications. In the case of Dositheos, he preserved the life of a man who will defile the Temple. He becomes a stranger and an alien to his God and his people as a result.
How would this warning be understood by Diaspora Jews in the Roman world?