In the chapter "Nirvana" of The Revolution of Beelzebub the inclusion of the Causal body among the "Four Bodies of Sin" shouldn't be taken as a definition. That would be inconsistent with the rest of Master Samael's teachings. "The Four Bodies of Sin" commonly refers to: Physical, Vital, Astral, and Mental bodies, not the Causal body. So you will also find in The Revolution of Beelzebub the following: "[the Essence]...is the small spark of consciousness which descends from the Human Soul [the Causal Body] into the Four Bodies of Sin (mental, astral, vital, physical)." This is how it is normally understood.
In the passage about the Dhyan-Chohan, reference to abandoning the Causal Body makes perfect sense. However, its inclusion among the "Four Bodies of Sin" is a quirk. The point in question has serious ramifications for the Gnostic esoteric work, since the mental, astral, vital, and physical bodies comprise a microcosm of the Law of 3 unto themselves. This lower quaternary is represented as the Four Elements, those aspects of Nature we have to master within ourselves, related to the 3rd, 4th, and 5th dimensions.
(Why does the lower quaternary, although a manifestation of the Law of 3, have four expressions? Because the 3rd dimension, in this top down view, is an aspect of the 4th dimension or Vital World.)
The Causal body the 6th dimension, belongs to another Triad of Creation, the Monad. Superior Manas, Tiphereth, the Human Soul, exists beyond good and evil. Having direct knowledge of Reality, it differs fundamentally from its reflection, the Inferior Manas in the Lower Quaternary, where Sin is due precisely to ignorance.