The outline of all the letters is precisely determined. Every detail of the letters is a geometrical symbol of a certain spiritual quality, produced by the combination of bestowal and reception. That is why Hebrew writing has remained unchanged over the course of millennia. All other alphabets changed with time, sometimes even to the point of becoming unrecognizable, whereas the forms of the Hebrew letters are fixed by the combination of spiritual forces and are therefore preserved throughout the centuries.
The horizontal details of the letters’ outlines symbolize the influence of the Light of Hassadim, while the vertical ones symbolize the influence of the Light of Hochma. Hassadim belongs to the force of Bina, while Hochma belongs to the force of Malchut.
This can be compared to an oscillograph, whose signal is also made up of the interaction of two scales. In fact, all the pictures in our world are also based on the combination of two forces, although there is also chronological development superimposed on them. This is caused by the intrusion of Klipa, which “stretches” the process in time. As a result, a difference emerges between the beginning and the conclusion.
To the degree we correct the forces of impurity, they join the single whole, bringing the initial and final states closer until reaching total unity. Then the very notion of time disappears.
From the 1st part of the Daily Kabbalah Lesson 12/15/10, The Zohar