Nefesh HaChayim, Reb Itzele's Long Annotation

This means that just as He (blessed be His name) is called “God-Ei”l who makes Himself hidden”493Heb.: Ei”l mis-ta-teir—Mis-ta-teir (hiding Himself) is the second term Reb Itzele used to denote a level of inaccessibility. “Hidden” is not as absolutely sealed away/inaccessible/not perceivable as “sealed away” (sa-toom). (Yeshayahu 45:15), even though the worlds were created having many levels, relative to them He didn’t change. It’s only relative to them that He makes Himself hidden, so that it will appear to us that His actions have many levels, and so that we’ll grasp His (blessed be His name) unity from within the hidden-ness of the lowest level.