The Rebbe taught this discourse on Shabbat Toledot  which was the eve of Rosh Chodesh (New Moon of) Kislev in 1953.  On the eve of the New Moon, the moon is hidden.  Then a thin sliver of moon is visible on the next day, actual Rosh Chodesh.  The discourse discusses the idea of the ‘essence’ which is dark, compared with the ‘gleam’ which emanates from the essence, which gives light.  The discussion of ‘light’ then leads to a discussion of love, love or light from above to below and from below to above.  These two kinds of light (Or, numerical value 207) are included in the word Ve-ahavta ‘and you shall love’ (numerical value 414).  This leads to a discussion about the relationship between Groom and Bride, and the blessings said under the Chupa, and one remembers that in the month of Kislev is the wedding anniversary of the Rebbe and his wife Chaya Mushka.  Now one thinks of the Groom giving joy to his wife, but in the future, both the Groom and the Bride will embody an ultimate joy, and the Bride will be a crown to her husband, higher than him. Ultimately, the Essence will shine.