Midrash sur L’Exode 20:22

Neither shalt thou go up by steps unto mine altar, that thy nakedness be not uncovered thereon (Exod. 20:23). A logical conclusion may be derived from these words. If in regard to a stone, which understands neither good nor evil, the Holy One, blessed be He, warns you not to shame it, how much more (should you not shame) your companion, who is formed in the likeness of the Holy One, blessed be He. For if thou lift up thy tool upon it, thou hast profaned it (Exod. 20:22). From this verse they argued that since the altar was created to prolong the life of man, while the iron blade shortens it, it would not be fitting to use a thing that shortens life upon that which prolongs it.