What is the history and significance of the Alter Rebbe’s ksav?

In the era of the Maggid, chassidim had tefillin with Ksav Arizal, generally identical to the Ashkenazic Ksav Beis Yosef, except for variations in several letter shapes to conform to the views of the mekubalim (see issue 855).

At some point, the Maggid instructed the Alter Rebbe to fine-tune a ksav that would satisfy both the halachic and kabbalistic requirements, and the Alter Rebbe did so.¹ The Alter Rebbe taught this ksav to the sofer R. Reuven of Yanovitch, who wrote the Alter Rebbe’s tefillin and mezuzos, and who in turn transmitted it to subsequent generations of sofrim.² This tradition differs somewhat from the Alter Rebbe’s description of the letter forms in his Shulchan Aruch.³

From the Tzemach Tzedek’s teshuvos, it’s clear that the Alter Rebbe’s ksav was in use in his time.⁴ The Rebbe Maharash wrote several megillos in the Alter Rebbe’s ksav (though the one in the Rebbe’s library was touched up at a later point without preserving the precision of the original ksav). The Frierdiker Rebbe had tefillin in Alter Rebbe’s ksav, purchased tefillin in this ksav for his sons-in-law, and sent a Torah to Kfar Chabad written in this ksav.⁵ (Moshiach’s sefer Torah was commissioned from a sofer in Eretz Yisroel who wrote Ksav Arizal since no Chabad sofrim were available at that time.)

From his arrival in America through the early years of the nesius, the Rebbe tried to track down any remaining sofrim with an unbroken mesora of the Alter Rebbe’s ksav. Although one can try to work out the ksav from the STaM that we have,⁶ the Rebbe notes that it’s hard to figure out what are the defining components dictated by the Alter Rebbe and what are just stylistic nuances from the sofer’s handwriting. Sadly, following the great destruction of WWII and Stalinist Russia, no sofer who could clarify all these doubts was found.⁷ (The standardized ksav Arizal in use today is likewise not based on an unbroken oral tradition.⁸)

Despite this, the Rebbe encouraged sofrim to learn to write in Alter Rebbe’s ksav, and for people to purchase tefillin and mezuzos with this ksav.⁹

When purchasing ksav Alter Rebbe, it’s important to buy from a sofer who knows this ksav well and knows how to write it properly.¹⁰ And only such a sofer should check the tefillin since others may treat certain changes as faults.

See Sources (open PDF)