Good question ! This is the best explantion here:

********THE FIRST MOUNTAIN OF INITIATION. ***********

(From Gnostic Author).

The first day of Jonah within the great fish (Leviathan-Lucifer) is the First Mountain of Initiation, Alchemical Birth. The second day is the Second Mountain, Mystical Death, at the end of which is Resurrection. The third day within the great fish (Leviathan-Lucifer) is the Third Mountain, Sacrifice. Thus, after three days Jonah is a resurrected Master. He lives in harmony with the Great Law and is ready to do the work of his Father as an awakened avatar of the Christ. He is “vomited” upon dry land, because he is no longer permitted to work within the waters of Alchemy. The proper use of the sexual force that was utilized to create the Twice Born is now prohibited to him. The work of the seven days of creation of the true Human Being is complete and the sex belongs to the Monad now.

Remember the Saviors of countless traditions who were cast into the waters as infants: Moses, Perseus, Karttikeya, Romulus and Remus, Maui, etc. Nor should it be forgotten the many Saviors born from stone (the philosophic stone/liquid stone of Mercury = the waters of Yesod): the Persian Mithras, the Babylonian Enkidu, the Chinese Qi, the earliest Norse Gods, etc. The Apache Savior is even named “Child-of–the Water” as a direct reference to the means of his (Alchemical) birth. It is within the waters (of Yesod) that the real Human Being is born.

Read more
gnosticteachings.org