The major theme of sefer Vayikra is, arguably, that of tumah and taharah, purity and impurity. When one reads the Torah, one senses what seems almost an obsession with this topic. If one happens to violate the special sanctity of the Temple, or of sacrifices, or even of the camp of Israel, the penalties are severe and harsh.
“Do not desecrate My holy name. I must be sanctified among the Israelites" (Vayikra 22:31).
When we think of the most important parts of the Torah we may think of the aseret hadibrot, the shema or the mitzva to love your neighbour as yourself.