וְלֹֽא־תַעֲלֶ֥ה בְמַעֲלֹ֖ת עַֽל־מִזְבְּחִ֑י אֲשֶׁ֛ר לֹֽא־תִגָּלֶ֥ה עֶרְוָתְךָ֖ עָלָֽיו׃ (פ)
Neither shalt thou go up by steps unto Mine altar, that thy nakedness be not uncovered thereon.
Read kabbalistic (mystical) interpretation of Exodus 20:23: and classical mystical sources.