The spread of Daat through the body.
Daat spreads through the body of Zeir Anpin (Z"A) — the operational mechanism by which the bridging Mochin performs its three-fold bridging.
Op. 126 closes the Daat of Z"A unit by specifying how Daat spreads through Z"A's body. The spreading is the operational mechanism by which Daat performs its bridging function.
Daat's spread is structural-anatomical. Daat starts in the upper Mochin region of Z"A's anatomy, then propagates downward through the body — through Chesed, Gevurah, Tiferet (CGT) (Chesed, Gevurah, Tiferet, the middle anatomy), through Netzach, Hod, Yesod (NHY) (Netzach, Hod, Yesod, the legs), to Malchut at the base. At every anatomical level, Daat is present and bridging — connecting the upper Mochin to the lower anatomy at that level.
The operational consequence: Z"A's complete governance is possible because Daat has spread through the body. The Mochin's fixing in Z"A — their structural integration with the body — depends on Daat's spread. Without Daat through the body, Z"A's Mental Powers would remain at the upper anatomy, and Z"A's CHaDaR governance through the body would be impossible.
Op. 127 (Tzelem doctrine — the complete Mental Powers entity is ten-fold, with Inner and Encompassing aspects). Op. 138 (the closing operational mechanism — operating throughout the Tzelem-completed Z"A anatomy).