The bleakest fast of the Hebrew calendar is on the ninth of Av, Tisha Be'av, commemorating the destruction of both Temples in Jerusalem (in 586 BCE, and 70 CE). We begin working ourselves up to feeling the enormity of the loss three weeks before, on the 17th of Tamuz, with a sunrise-to-sunset fast on the date the Roman armies breached the wall around Jerusalem. From the 17th of Tamuz until Tisha Be'av, Jewish law ordains a moratorium on all group festivities, with no haircuts, no shaving (although some may continue to shave until the beginning of Av) or listening to music. The expressions of mourning grow in intensity with the start of Av, when we do not wear freshly laundered clothing (except for those garments which absorb perspiration), and do not eat meat or drink wine other than on the Sabbath. And then, on Tisha Be'av itself, we fast for 25 hours (from before sunset until the coming out of the stars the next night), sit on the ground or on a low stool as we read the Scroll of Lamentations in the evening and recite dirges until midday; we do not even refresh ourselves with the balming waters of Torah except for those passages which deal with the destruction or laws of mourning. The prohibitions of meat and wine, and even laundering garments, extend into mid-day of the 10th of Av, when the majority of the Second Temple was actually destroyed by Roman flames. But what precisely is it that we are mourning when we beat our breasts and weep over the destruction of the Temple? It cannot be the loss of the mere buildings, no matter how grand. After all, the Jews had already rejected the massive Egyptian pyramids in favor of two modest tablets of engraved stone. It cannot even be the loss of our national sovereignty (which the loss of the Temples symbolized), because if so, the our fast would be on the anniversary of the removal of the Judean kings and the installation of a Roman governor in Jerusalem, which took place decades before. And it certainly could not have been the loss of the sacrifices, which disappeared together with the Temple. Prayers and repentance seem to be a fine substitute for sacrifices, and there are statements in the midrash and in Maimonides's Guide for the Perplexed which suggest that they are even improvements over them. Rabbi Avraham Yitzhak Hakohen Kook maintains that in the third temple the only sacrifice will be the meal offering (at the end of the morning reading about the daily sacrifices). So what is it about the loss of the Temple which engenders such national mourning? I would submit that the Holy Temple was inextricably intertwined with our national mission, our national reason for being: to be God's witnesses, and thereby serve as a light unto the nations, bringing humanity to the God of justice, morality and peace. Our prophets saw the Temple as the living example from which all nations could learn how to perfect society. With the loss of the Temple, we ceased to be "players" on the world stage; we lost the means by which our message was to be promulgated. And a world without compassionate righteousness and just morality - especially with the possibility of global nuclear destruction - is a world which cannot endure. At the very dawn of Jewish history, when Abraham was elected by God, he was given a divine charge: "through you shall be blessed all the families of the earth" (Genesis 12:3). The Lord then seals a covenant with him, (Gen. 15) guaranteeing that he will be the father of a great nation, even the father of a multitude of nations (which will all accept ethical monotheism). And then the sacred text explains why Abraham was elected: "Through [Abraham] shall be blessed all the nations of the earth; the reason that I have known, loved and designated (Abraham) is in order that he command... his household after him to guard the way of the Lord, to do compassionate righteousness and just morality..." (Gen. 18:18, 19). This charge is repeated to Abraham after the binding of Isaac (Gen. 22:17, 18). In effect, the Bible is saying our mission can only be accomplished if we are willing to sacrifice the lives of our children for it, and it will disseminate to the world from "the mountain from whence the Lord will be revealed" (ibid 14). When Jacob leaves his ancestral home (fleeing Esau's wrath) and dreams his dream at Beth El, he envisions a ladder rooted in the earth and reaching up to the heavens - a veritable Holy Temple, beit hamikdash; "he is blessed that his seed shall spread out westward, eastward, northward and southward, and through him shall be blessed all the families of the earth." Jacob identifies the ladder as "the house of God, at the gates of the heavens," and Rashi, citing the talmudic sages, insists that the ladder extended to the Temple Mount (Gen. 28:12, 14, 17 and Rashi ad loc). In the Book of Exodus, at the Song of the Sea, when the text describes the awe of the nations at the Lord's wondrous miracles in freeing the enslaved from tyranny, the Israelites sing of being brought to and planted within the Temple Mount, when the Temple of the Lord will be prepared by divine hands, and the Lord will reign throughout the world (Exodus 15:17, 18). And when King Solomon dedicates the Temple in Jerusalem, he beseeches God to answer the prayers of the gentiles who shall come from far away "for Your name's sake," so that "all the nations of the earth may recognize Your name, as does Your nation Israel" (I Kings 8:41-43). And, in order to close the circle, when we read the prophetic portion of Isaiah this Shabbat (Hazon, Isaiah ben Amotz), who weepingly excoriates the Israelites for having forgotten their ethical calling, for their treatment of ritual as substitutes for loving-kindness and justice and thereby their having to suffer the destruction of the Temple, he promises that in the future "Zion shall be redeemed by moral justice, and those who return to Zion shall practice compassionate righteousness" (Isaiah 1:27). The second chapter of Isaiah, a continuation of the vision we have just cited (Isaiah 2:1), pictures the Temple exalted above the mountains, inspiring the nations to "beat their swords into plowshares, their spears into pruning hooks." Indeed, we yearn for our Temple, which will inspire the world to accept a God of love, morality, compassion and peace. The writer is the founder and chancellor of Ohr Torah Stone Colleges and Graduate Programs, and chief rabbi of Efrat.