One of the chasidim of the holy Alter Rebbe, while in Lyozna or Liadi, needed to pass through Yanowitz and return shortly afterwards to the Alter Rebbe. The Alter Rebbe requested that when he passed through Yanowitz, he should stop by the scribe Reb Reuven and ask him to write mezuzot for the Alter Rebbe’s use. On his return, he could receive the mezuzot from the scribe and bring them to Lyozna to the Alter Rebbe.
The chasid carried out the mission and asked Reb Reuven to write mezuzot for him as well. The scribe agreed, and when the chasid returned to collect the mezuzot, the scribe gave him two packages, saying: "This package is for the holy Alter Rebbe, and this package is for you." When the chasid came to the Alter Rebbe, he was curious to know why the scribe had divided the mezuzot into two packages. What was the difference between them?
Out of confusion, the chasid took the package that the scribe had given him for himself and gave it to the Alter Rebbe. The Rebbe examined them and said: “Why did he start sending me such mezuzot?” The chasid realizing there was a problem suggested, “Perhaps it is I who made a mistake, as he wrote mezuzot for me too, and I have another package!” The chasid gave the Rebbe the second package. The Rebbe examined them and said, “Yes, yes, this is good.” The chasid, traveling again through Yanowitz on his way home, stopped at the scribe’s house and complained, “Why didn't you write the mezuzot properly for me? I know because the holy Alter Rebbe did not want to accept the mezuzot you wrote for me.” Reb Reuven the scribe said: “Your mezuzot were written with identical intentions as the Rebbe’s. But the Rebbe insists that his mezuzot be written when the moon is full, which I did not do for yours.”
The wondrous instruction revealed in this story, that mezuzot be written during a full moon, does not appear in any written halachic or Kabbalistic book. This is a unique practice instructed by the Alter Rebbe. Nevertheless, from the words of the Kabbalists about the moon and the mezuzot, we can trace something of this connection.
First, the moon is a symbol of the sefirah of kingdom (malchut). Second, numerical value of mezuzah (מְזוּזָה) is the same as God’s Name Adni (אֲדֹנָי), the Name associated with kingdom. Third, the mezuzah is affixed to the doorpost of the house, associated with kingdom, which serves as the threshold of the door from the three lower Worlds to the World of Emanation. Thus, for several reasons, the moon is closely connected to the mezuzah. But what is the significance of the full moon specifically?
The sefirah of kingdom in the World of Emanation is the Shechinah, the Divine Presence that emerges from the doorway of its home into the three lower Worlds. When the moon is full, on the 15th night of the month, it alludes to the time when the Shechinah, which is also the source of the souls of Israel, is complete and full. This was the case in the time of King Solomon—whose name hints at completeness (shlemut) and who was the 15th generation from Abraham—and so it will be in the time of redemption, when the light of the moon shall be like the light of the sun. The people of Israel and the Shechinah will become radiant and illuminating like the Almighty without any shadow obscuring them. This is the light that the Alter Rebbe wants to feel in his mezuzot—mezuzot of a full moon.
