Part 10 · Chapter 120

And behold, it is in this way: in each of these two [instances of] Ehyeh, there are 42 letters including the Kolel: 4 in the simple filling, 10 in the filling, and 27 in the filling of the filling — thus 42 twice in the two mentioned [instances of] Ehyeh. This is the reason Bina is called Ima [mother]: by the secret of the Ehyeh within her, which has 41 letters — spelling Em, mother.