Assorted sources showing that Light Unto the Nations applies before Moshiach
(bold lettering added here for emphasis)
R' Hirsch, Psalm LXXXIX
"This 'teaching ode' also looks with confidence to deliverance from the anguish of the Exile, but from a point of view different from the one expressed in Psalm 88. While Psalm 88 tells us to trust in eventual redemption because of Israel's survival throughout the troubles of Exile, Psalm 89 teaches us to have faith because of the Divine promises linked with the election of David and his descendants.
"Verse 3 contains the thought that the universal salvation which God in His mercy has appointed for Israel and mankind in general indeed still lies in the future. It must be remembered, however, that the building of this future goes on ceaselessly even now, and that every event that Heaven decrees to happen on earth is nothing but a manifestation of God's faithfulness, which guides and trains us for this goal of ultimate salvation. Side by side that salvation, and closely linked with it, there is the promise pertaining to David, to the fulfillment of which the whole course of history is dedicated (Verse 4,5).
"This faith is founded upon the unlimited omnipotence of God in nature and history (Verses 6-14), upon the right and order which the basis of all of God's reign, and upon the loving-kindness and truth which are the goals of His Providence (Verse 15). From this (see Verses 16-19) the Psalm proceeds to the ideal state of salvation which is certain to come to every human society and also to Israel in particular, once it accepts and adopts as its own this recognition of God's will and sovereignty, and once it subordinates every aspect of its life, both individual and communal to God's guidance.
"God has chosen David, and his descendants, who do not forfeit this mission despite temporary straying, to be His co-workers in behalf of the goal of salvation that is dependent upon the spiritual and moral ennoblement of men and nations (Verses 20-38). At the present time, contrary to the expectations fostered by God's promises, the kingdom and sanctuary of David lie in ruins (Verses 39-46). But only one glance at the depths of impermanence and vanity into which mankind would sink were it bereft of the spirit of David, will suffice to assure us that God will surely come forth again and complete the work which He had begun with Israel and David. (Verses 47-50). For Israel is still in the service of God (see Verses 51-53) and bears within its bosom the future of all the nations, so that Israel's troubles are simply the birthpangs of the dawn of the morning that is to come to all mankind. Israel's enemies are the foes of the kingdom, and their very abuses are the footsteps of the coming Messiah."
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R' Hirsch, Collected Writings, Vol. VII, p. 269
“It was a Jew with his lyre, David with his harp, who from the very beginning perceived himself as participating in a historic mission to all the world, sounding his harp in order to stir all the nations to recognize God and to worship Him with devotion (II Samuel 22, 50; Psalms 57, 10; 108, 4).
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R’ Avidgor Miller, Behold A People, p. 285
“Yet despite the perfect legitimacy of this marriage, it earned the censure of G--d: "When Shlomoh took the daughter of Pharaoh, Gabriel came down and set a stick into the sea, upon which mud collected; and upon that was built the great city of Rome" (Shabbos 56 B). But this censure was not for the act, for it did not prevent Shlomoh from attaining the highest perfection in his career: the two visitations from G-d. Had the subsequent developments continued according to Shlomoh's plan, the union with the daughter of Pharaoh could have achieved the greatest results for the honor of G-d; for this wise monarch planned to induce the nations to cast away their idols and to accept the true G-d. In this, Egypt would have shown the way, just as had been the Case at the Exodus when a great number of their choicest families had joined Israel. There were good reasons to expect success, for Shlomoh had gained great admiration among the nations; and his policy of marriage unions with many monarchs was part of a grand plan which would have succeeded, had not the weakness of old ege (like his father's) prevented him.”
(R' Miller explains on one of his tapes that Shlomo married these princesses in order to influence their fathers to abandon idol worship).
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The following sources and explanations are by R' J Dovid Bleich, Tikun Olam, Jewish Obligations, Tikun Olam, The Orthodox Forum
Netziv, Introduction to Shemos
He explains that the book of Shemos complements the book of Bereishis which declares Israel to be the tachlis of creation. Israel does not achieve this goal "until Israel excited from Egypt and achieved their purpose that they be fit to be an illumination unto the nations to cause them to arrive at knowledge of the Lord of the Universe."
(They are fit for this illumination after Har Sinai. The matter does not wait unto Moshiach)
Netziv Ex. 12:51
"And it came to pass the selfsame day that God brought the children of Israel out of the land of Egypt al tzivotam." The Netziv translates al tzivotam to mean "for service of" which is "to be an illumination unto the nations to cause them to arrive a knowledge of the Lord of the universe." They were fit for this purpose only after bris milah and the Exodus.
(He does not say they were fit only after Moshiach)
Malbim, Isaiah 2:2-3
"Come ye, let us go up to the mountain of the Lord, to the house of the God of Jacob and he will teach us His ways (derakoav) and we will walk in his paths (orhotav). The Malbim defines "ways" as major roads and paths as secondary roads. He says the Jews will teach the nations the "roots and principles" of divine service and in the end of days the gentiles will seek greater edification and learn the byways.
(This suggests active teaching in the millennium before Moshiach).
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Rav Kook on “Light unto the nations” Now or After Moshiach
Mikeitz: Joseph and Judah
"The strife among Jacob's sons centered on two conflicting viewpoints vis a vis the sanctity of the Jewish people. Judah felt that we need to act according to the current reality and that, given the present situation, the Jewish people need to maintain a separate existence from other nations in order to safeguard their unique heritage. Joseph, on the other hand, believed that we should focus on the final goal. We need to take into account the hidden potential of the future era, when "nations will walk by your light" (Isaiah 60:3). Thus, according to Joseph, even nowadays we are responsible for the spiritual elevation of all peoples. So which outlook is correct - Judah's pragmatic nationalism or Joseph's visionary universalism?
"The Present versus the Future
"The dispute between Judah and Joseph is in fact a reflection of a fundamental split in the world. The rift between the present reality and the future potential is rooted in the very foundations of the universe. On the second day of Creation, God formed the rakia, the firmament separating the waters below from the waters above (Gen. 1:7; see Chagigah 15a). This separation signifies a rupture between the present (as represented by the "lower waters" of this world) and the future (the "higher waters" of the heavens). The inability to reveal the future potential in the present is a fundamental defect of our world; unlike the other days of Creation, the Torah does not describe the second day, when this breach occurred, as being "good."
"Joseph and the Letter Hey
"According to the Midrash (Sotah 36b), the angel Gabriel taught Joseph seventy languages. Gabriel also added the Hebrew letter hey from God's Name to Joseph's name, calling him "Yehosef" (Ps. 81:6). What is the significance of this extra letter?
"The Sages wrote that God created this world with the letter hey, and the World to Come with the letter yud (Breishit Rabbah 12:9). In Joseph's view, each nation is measured according to its future spiritual potential, according to how it will fit in the final plan of kiddush ha-Shem, the sanctification of God's Name and revelation of His rule in the world. The particular role of each nation is indicated by its unique language. Without the letter hey, however, Joseph could not properly grasp the language of each nation, i.e., he could not ascertain the nature of their role in the future world. With the addition of the letter hey to his name - the letter used to create this world - Joseph gained the ability to understand the universe as it exists now. Joseph was then able to comprehend the languages of all peoples and assess their spiritual potential.
"Joseph was able to discern the world's potential for kiddush ha-Shem with the help of a single letter. He used the hey, a letter which is closed from three sides, as this future potential is currently almost completely hidden. Judah, on the other hand, looked at the world's spiritual state as it is revealed now.
"Joseph, who sanctified God's Name in private, merited one letter of God's Name. Judah, who sanctified God's Name in public, merited that his entire name was called after God's Name" (Sotah 36b).
"Two Types of Tzaddikim
"According to the Zohar, Benjamin complemented his brother Joseph. "Rachel gave birth to two tzaddikim, Joseph and Benjamin. Joseph was a 'higher tzaddik,' while his brother Benjamin was a 'lower tzaddik'" (Vayeitzei 153b). What are these two types of saintly tzaddikim?
"The "higher tzaddik" is a conduit for the shefa (the Divine influence), drawing it down from above, while the "lower tzaddik" passes the shefa to the physical world below. Benjamin's role, as the "lower tzaddik," was to imbue our world with holiness. His whole life, Benjamin was concerned that the Temple should be built in the portion of Eretz Yisrael that his tribe would inherit. Why was that so vital to Benjamin?
"The Temple is "a house of prayer for all peoples," allowing all to share in its holiness. "Had the nations known how important the Temple was for them, they would have surrounded it with forts in order to guard over it" (Tanhuma Bamidbar 3). The Temple has a fundamental role in Joseph's universal outlook.
"The Monarchy and the Temple
"The dialectic between Judah and Joseph finds expression in two institutions: the monarchy and the Temple. The monarchy, whose role was to protect the national sanctity of the Jewish people, was established in Judah's inheritance, in Hebron and Jerusalem. The Temple, whose role was to elevate all of humanity, was built on Benjamin's land. Yet the Temple was partially located on a strip of land that extends from Judah's portion into Benjamin's portion. This strip represents the synthesis of Judah and Joseph, the integration of the national and universal viewpoints.
"Mikeitz, the name of the Torah reading, means "at the end." The Midrash Tanchuma explains that God established an end for all things. Just as Joseph's imprisonment ended in Mikeitz, so too, the conflict between Judah and Joseph will be resolved after a constructive period of development and change. The fundamental dissonance in the world will be repaired, and the rift between the present and the potential, between the lower and higher waters of creation, will be healed."