Copied from a manuscript of Baal HaSulam
In the matter of the seven full ones of the Sanctification of the New Moon, it is customary to wait for seven full ones, and the end of Shabbat [Sabbath], too. It is not like the custom that if the end of Shabbat occurs in the middle of the seven days, we sanctify the moon, or when the seven days have been completed from the time to the time, they do not wait for the end of Shabbat. This is not so, as we should wait the full seven, specifically on the end of Shabbat.
The thing is that the moon is considered Malchut, called “seventh,” which is “He is in me.” This means that when the Shabbat is filled by the six workdays, called “He,” the Shabbat says, “He is in me.” “He” is the sun, and “me” is the moon, which receives all of its light from the sun, and has nothing of its own.
However, there are two Behinot [discernments] in it, called “Shabbat” and “Month,” since Malchut herself is regarded as the four known discernments HB and TM. The first three Behinot (Hochma, Bina, Tifferet) are the Shabbat. These are the three meals, called and implied in the Torah in the three times “this day.” Indeed, Behina Dalet in her is the end of Shabbat or month, and it is not included in the “this day,” as she is night, and not day.
We could ask, “The first meal of Shabbat is night, too, so why does the Torah call it ‘this day’?” However, the eve of Shabbat is “And there shall be one day which shall be known as the Lord’s, neither day, nor night; but it shall come to pass that there shall be light at evening time.”
However, the night of the end of Shabbat is still dark, and not light. Hence, our sages instructed us in the oral Torah to set up a table at the end of Shabbat, too, to correct this darkness and night, which are still uncorrected. This is called “Melaveh Malkah” [escorting the Queen], sustaining and complementing that Luz bone, which is Behina Dalet, which does not receive anything from the three meals of Shabbat. Yet, this Behina Dalet is gradually completed by way of “the month, the day.” This is the meaning of the sanctification of the month, that Israel sanctify the times, meaning that residue that is not nourished by the meal of Shabbat.
Hence, even the greatest among the priests, of which there is none higher in Kedusha [holiness], is warned to caution not to defile any dead from among his relatives. The writing warns him: “except for his kin, … for her may he defile himself.” From all the above, you can understand that any upper Kedusha comes from Shabbat. And since that Luz bone, meaning Behina Dalet, called “his kin,” does not receive from the Shabbat meal, the great priest is not exempted from being defiled by it.
Indeed, the meaning of the correction in the sanctification of the month extends from the Shabbat and its illuminations. This is the meaning of “Moses was perplexed, until the Creator showed him the similitude of a coin of fire and told him, ‘Thus behold and sanctify.’” This means that Moses was very confused because he could not sanctify it, since all the power of Moses is the Shabbat, since the Torah was given on Shabbat.
Hence, he could not find a correction to this residue in all the lights of the Torah, since this residue is not fed by all that. This is why Moses was perplexed.
And what did the Creator do? He took it and molded in it a shape within a shape, like a coin of fire, where the shape imprinted in its one side is not like the shape on the other side, as our sages said about the coin of Abraham that an old man and an old woman were on its one side, representing Behina Bet, the quality of mercy, and a young man and a virgin on the other side, which are Behina Dalet, the harsh quality of judgment, from the words, “neither had any man known her.”
These two forms were joined in such a way that when the Creator wants to extend a correction of the lights of Shabbat there through the work of the righteous, the Creator shows the righteous that shape that extended from the first three qualities of Malchut, which we call Behina Bet, and which the righteous can sanctify with the lights of Shabbat. This is the meaning of…