With this parashah begins the reading and analysis of the third book of the Pentateuch, which the Talmud (Mishnah Megillah 3: 5) calls Torat Kohanim, the Treatise on Priests, and whose name was translated into Greek and Latin as: the text of the Levites, Leviticus. The priests (kohanim), descendants of Aaron, brother of Moses, were of the tribe of Levi, and in the Talmudic literature and Greco-Roman texts of that time both, kohanim and leviim, were used interchangeably.
Much of this book contains procedures about the sacrifices that were to be offered to God. Sacrifice in Hebrew is Korban, whose root is KRB, the same as that of the verb to approach. According to the biblical narrative, it appears that from the beginning human beings understood that, in order to approach God, they should bring some offering of the fruits of their labor, as did Cain and Abel (Genesis 4: 3-4), Noah, on leaving the ark that rescued him from the flood (Genesis 8: 20-21), and Abraham when settling in Canaan (Genesis 12: 7).
According to Maimonides (Guide to the Perplexed, Chapter 32), sacrifices were the way in which men of the past understood how they should approach God. He believed that the laws of the Torah only came to restrict sacrifices exclusively to the God who was revealed at Sinai and to eradicate certain abject practices that were common among many peoples, such as human sacrifice (Leviticus 18:21).
In the books of the prophets, as well as in the Talmud, there are many passages that emphasize that worship is merely a ritual which people must make meaningful by acting with righteousness, justice and mercy. As Micah eloquently stated (6: 6-8):
With what will I stand before the Lord, and worship the God of the highest? Will I come before him with burnt offerings, with yearling calves?
Will God be pleased by thousands of rams, or by myriads of streams of oil? Shall I give my firstborn to atone for my transgression, the fruit of my bowels for the sin of my soul?
He has declared to you, oh man, what is good, and what God demands of you: Only to do justice, and to love mercy, and to walk humbly with your God.
Every ritual that seeks to help the individual to approach the Creator is meaningless without these three behaviours.