The Three Levels of the Ark

תחתים שנים ושלישים תעשה
Rashi explains; the lower level for garbage, the second level was for animals and חיות and the upper level for people. The lower level is referred to forbidden lust that a person must מאוסות - dislike, like garbage. The second level is permitted actions that should be like a secondary, like beheimos and חיות – animals and living creatures, that are secondary to man. The upper level is for people that their main service should be for things that are pertaining to the soul of the person.

Sabah Kadisha of Slonim – Toras Avos