"And it happened on the eighth day, that Moses called Aaron and his sons, and the elders of Israel" ( Leviticus 9:1 ) Our biblical portion of Shemini opens: "And it happened on the eighth dayâ€¦," with Rashi commenting: "the eighth day of the consecration ceremonies of the Sanctuary, the first day of the month of Nisan, the very day on which the Sanctuary was erected." And it was on this eighth day - in the midst of the exultant celebration following the descent of a divine fire which consumed the offering on the altar as a sign of heavenly acceptance that Nadab and Abihu were also consumed by divine fire! What occasioned such divine wrath, and what is the significance of the eighth day, which gives the portion its name? Moreover, what is the symbolic secret of fire, which makes it a statement of both divine acceptance and divine disfavor, God's grace and God's wrath? And finally, we conduct the havdala ceremony every Saturday night (the beginning of "the eighth day" of the week) around a flame. Why do we look at our fingernails on making the blessing over fire? The "eighth day" is indeed fraught with significance. Let us return to the initial seven days of creation. On the sixth day God created the human being and placed him - Adam together with his wife Eve - in the Garden of Eden. The first couple sinned by eating the fruit of the tree of the knowledge of good and evil, by declaring themselves and not God the arbiters of good and evil, thereby subjectivizing morality. And so Adam and Eve were banished from Eden. Then came the first Sabbath Day, when each individual can find refuge under the wings of the Divine Presence, the day when the Almighty especially extends his arms to embrace the penitent. Indeed the Midrash teaches us that Adam recited the Psalm for the Sabbath Day, uplifted by the understanding that there is truly a road back to Eden, and that it is paved with repentance. And then came the first Saturday night, the beginning of the first eighth day: "This was the first time that darkness began to descend on the worldâ€¦. And the Almighty prepared for Adam two flint stones; Adam rubbed them together and there emerged fireâ€¦." (Bereishit Rabba 11,2). Hence the first eighth day, the beginning of the second week, became parallel to the first day of creation, since God had then created light for the world, and on the eighth day Adam created light and warmth for the world. But it is much deeper than that. In the seven days of creation, God created a world for human beings; on the eighth day, Adam discovered - through fire - how he could repair that world, improve that world, re-create that world as a true picture of the Divine. And if in the seven days of creation, God made a world for humanity, on the eighth day of the consecration of the Sanctuary the Israelites made a sacred space - an improved world-in-miniature - in which God could dwell together with humanity: "They shall make for Me a Sanctuary so that I may dwell in their midst" (Exodus, Truma). Fire is the human response to God's light. But fire is a two-edged sword; it can strengthen and purify, or it can subvert and petrify; it can bring light and warmth, or it can bring explosions and nuclear destruction. The blessing over fire, which acknowledges its ultimate Divine source, must remind us that we have to serve God in accordance with His laws, that we dare not remove our creativity from His direction. To do so would be a repetition of Adam's sin. God sent His divine light and fire as a sign that He accepted our Sanctuary, the work of human hands - built exactly according to the Divine directions. Then Nadab and Abihu came along with "a strange fire, which they had not been commanded to bringâ€¦." Yes, we must use our creativity in the service of God to perfect ourselves and our world - but only in accordance with His will, in accordance with the limits He has placed on divine service, so that we never fall into the trap of bringing the strange fires of Moloch (Deut. 18:10) or the immoral explosions of jihad. Human hands created fire, but human hands are agents of free will, and can utilize that fire either as an agent of creativity (in cooking food, baking bricks and forging tools) or of destruction (fires of fanaticism and weapons of war). And so we look at our fingers as we make the blessing over fire every Saturday night. The usual explanation is that we can see in the reflection of the light on one side of our fingers and not on the other its power to enhance vision. Rabbi Menahem Meiri (citing the gaonim) suggests that when Adam was first created, his entire body was covered by nails as a protective coating; as a result of his eating the forbidden fruit, this protective layer was removed - with only the finger and toenails remaining as reminders of his earlier more protected state. Since we are soon to intone the prayer for the speedy arrival of Elijah, herald of Redemption, we are in effect requesting a return to Eden. I would maintain, however, that by looking at our fingernails as we make havdala we are reminding ourselves that the future of our lives and our world - indeed, whether or not we properly recreate our world and return to Eden - lies in our own hands and how we use the amazing powers of fire. The writer is the founder and chancellor of Ohr Torah Stone Colleges and Graduate Programs, and chief rabbi of Efrat.