The Six Abodes of Satan - Congregation Yeshuat Yisrael

Satan’s Sin was Pride
Pride, which is self-will, self-esteem, conceit, and
egotism, is the usual definition of Lucifer’s sin.
Lucifer’s self-will prompted him to unholy
ambition. He repudiated the Creator and
displayed dissatisfaction with the subordinate
position to which he had been appointed.
Lucifer’s ambition and self-promotion was used to
advance himself to the highest heaven and into
the likeness of the sovereign God of the universe.