[The regulations governing] release from vows hover in the air and have no [firm Scriptural] support. [Certain] laws of the Sabbath, chagigah, and me'ilah are like mountains suspended by a hair, for there are few Scriptural references and many laws. [The regulations governing] property law, the [sacrificial] services, purity and contamination, and illicit relationships have [firm Scriptural] support. All of these are essentials of the Torah.