The theological application of the book is found in its historical setting. For the Jews who returned to Jerusalem, the post-exilic books of Chronicles, Nehemiah, Ezra, Haggai and Zechariah specifically answered the larger theological question of that day, which was, “Are we still the apple of His eye (Deuteronomy 32:10b) and in a covenant relationship with Him?” The conflict between Haman, the Agagite and Mordecai, the Jew drive the reversal of fortunes at the end of the book. The seemingly insignificant detail that identifies Haman as an Agagite is the key that links the Jews of the Diaspora to the ancient covenant ADONAI made with their ancestors at Sinai, reassuring them of its continuing truth in their lives.
Agag was the king of the Amalekites at the time Saul was Isra'el’s first king (First Samuel 15). The Amalekites had the questionable distinction of being the first people to attack God’s people just after the Exodus (see my commentary on Exodus Cv – The Amalekites Came and Attacked the Israelites at Rephidim). Consequently, the LORD promised Moses that He would be at war with them from generation to generation until the memory of Amalek was blotted out from under heaven (Exodus 17:14-15).
The story of Esther is another episode of that ancient battle between Israel and the Amalekites, and it sure looked like the Jews would be annihilated. They had no king, no city, no army, no prophet, no land, no Temple, no priesthood and no sacrifices. They were but a small, defenseless minority living at the mercy of a ruthless and powerful pagan monarchy. Moreover, they found themselves in that dire circumstance because their sin had been just as bad as that of the pagan nations (Ezekiel 8). They could only expect the worst, and humanly, they only deserved the worst. But when Haman was impaled, and Mordecai was elevated to a rank that was second only to King Ahasuerus (10:3), it revealed that despite their sin and despite the fact that they were not in the Land, ADONAI's promise to Isra'el was still valid. He had said to Abraham: I will bless those who bless you, and whoever curses you I will curse; and all the peoples of the earth will be blessed through you (Genesis 12:3). The book of Esther shows us that the Jews were still under the watchful care of a loving God (Psalm 91).
Esther is perhaps the most striking biblical example of the providence of God. The word providence comes from the Latin providere, which literally means to foresee. But more than merely knowing about the future, the word carries the connotation of making preparation for the future. Thus, God operates behind the scenes to govern all circumstances through the normal and the ordinary course of human history, even without the intervention of the miraculous.
The book of Esther is the most true-to-life biblical example of the providence of ADONAI precisely because He seems absent. But even in the most pagan corner of the world, the LORD is controlling all things to the benefit of His people and the glory of His name. Even His own people, like Esther and Mordecai, made decisions that came from cloudy motives at best, or perhaps even outright disobedience, God still worked providentially through those very actions to fulfill His covenant.7 Surely Romans 8:28 is a New Covenant summary of the theological message of the book: And we know that in all things God works for the good of those who love Him, who have been called according to His purpose.