The code forms a large portion, approximately one third, of the commandments of the Torah, and thus is a major source of Jewish law.
Unlike the Decalogues, however, Yahweh speaks the laws to Moses while descended, in a cloud, upon the Tabernacle which the Israelites have constructed.
Critical scholars assert that in addition to this, over time, variations of detail would develop, authority for which must be committed to writing, so that actual practise would become justified by law.
Colophons, which, according to textual criticism, are best explained as survivals from previous collections, are found in parts of the priestly code, at Leviticus 6:7, 7:37-38, 11:46-47, 13:59; 14:54-57, and 15:32-33.
Leviticus 5:15-19 and 6:2-18 are usually regarded, under textual criticism, to have been from a continuous work, due to identical writing style, such as a ram without blemish out of the flock, with thy estimation ..., and trespass (ed) against the LORD.
Such rituals involve the idea that sin can be transferred, from the sinner to the living animal, via the blood of its dead associate.
These are generally considered to be amongst the oldest layer of laws, since they invoke extended supernatural ideas, rather than simply involving belief in a god.
In anthropology generally, as well as in biblical criticism, this is viewed as a later development, replacing conceptions of the supernatural with simply being fined for the sin.
Likewise, the ritual of the Red Heifer at Numbers 9:1-13, in which water of cleansing is produced, is generally thought by academic criticism to be early.
This change from more supernatural ideas methods to naturalistic ones is present also in aspects of law other than completely sacrificial rituals.
This segment offers even more precision, detailing the uncleanliness of objects which have made contact with carcasses, and is thus usually thought of, by critical scholars, as an even later addition than Leviticus 11:24-31.
Standard textual criticism, as well as the repetition, is thought to indicate that the second portion is by a different writer, creating an explanation that was not originally present.
While this is presented as being a response for poor sinners, critical scholarship interprets the section as indicating that, historically, an earlier sacrificial offering, of a lamb, was increasingly being replaced, over time, by a pair of turtledoves.
Another aspect of the "priestly teacher's" apparent style is a concentration on atonement for uncleanliness and sin, particularly via rituals involving "wave offerings".
Of these, Leviticus 15 is noticeably repetitive, repeating both bathe [itself] in water and be unclean until the even, for almost every verse, as well as the detail of the atonement sacrifice.
This chapter is therefore, under academic criticism, viewed as a late expansion of an earlier, much shorter, law, which simply laid out the basic rule that running issue of bodily fluids is ritually unclean, and contact with it, including with the person that possesses it, is ritually unclean, rather than detailing the atonement sacrifice, and listing examples of what constitutes contact.
Another distinct style is that of case law, in which the basic outline of a brief problem is described, such as Leviticus 15:32-41, discussing how to deal with a man who has collected sticks on the sabbath, and whether that constitutes a violation of the rule not to commit work on that day, and then the solution is explained by Moses, often after he has consulted with God.
While many of these instances have, according to textual criticism, the resemblance of a single source, there are nevertheless portions which appear to be later layers, such as the additional return to the daughters of Zelophehad in Leviticus 36 to discuss a slightly different matter.
The benediction at Leviticus 6:22-27 is viewed as a late addition to that chapter, including for linguistic reasons concerning the manner of wording used within it as dating from an historically later period.