The book of Leviticus, although written by a single priestly guild—the Aaronides—does nonetheless exhibit editorial reworkings and insertions of texts most likely written at different periods.
Two traditions seem to be intertwined in the opening chapters of Leviticus—one which acknowledges that the sacrificial law code was given at mount Sinai, and one which stipulates that it was given to Moses at the Tent of Meeting. Indeed one could argue that the Tent of Meeting sat at the foot of Sinai so there really isn’t much of a contradiction here. But in actuality it does look as though we have two different textual traditions, which were later edited together. Here’s how they might have originally stood.
Exodus 40:34-35 relates how, after the Tent of Meeting is erected on the New Year, Moses was not able to go into the Tent because of Yahweh’s presence. In Leviticus 1:1, we are informed that Yahweh spoke to Moses “from the Tent of Meeting.” Furthermore, the sacrificial legislation in Leviticus 1-5 is directed to the people: “Speak to the children of Israel and you shall say to them…” It is quite possible that this body of literature once existed as a separate document which instructed the people about bringing their sacrificial animals to the Aaronid priest before Yahweh’s altar, and in each case—the burnt-offering, the peace-offering, and the sin-offering—what to do.
Leviticus 6-7 is directed not to the people, but only to Aaron and his sons. In Leviticus 6:1 Yahweh tells Moses to instruct Aaron and his sons about how to perform each sacrifice. The sacrificial descriptions in Leviticus 6 & 7 are solely directed at the Aaronid priesthood, and they detail how to perform each sacrifice.
It is not a coincidence, then, that each of these two texts written for/to two different groups also identifies two different locales for the giving of these laws: from the Tent of Meeting (Lev 1-5) and at Sinai (Lev 6-7).
More problematic, and a contradiction which we have already dealt with (see #155), is that while the texts of Leviticus 1-7 portray Yahweh giving instructions and commandments about sacrifices to the wilderness generation, the text of Jeremiah 7:22 has Yahweh claiming the exact contrary.