Leviticus

What were the Urim and the Thummim? Mentioned in 8:8 and in various other OT passages, the Urim and the Thummim remain a mystery to modern readers. All that is known is that they were worn on the garment of the high priest, and were used in seeking the Lord’s will on particular matters.
The account of the ordination of Aaron and his sons as priests (8:1–36) is divided into seven parts by the phrase “as the Lord commanded.” The number seven often symbolizes completion in the OT.
Sin offerings atoned for unintentional sins (4:1–35) and for sins of omission (5:1–13). The sacrificial animal was burned “outside of the camp” (4:12), rather than at the base of the altar. This foreshadowed the sacrificial death of Jesus Christ, who was crucified “outside the camp” (Heb. 13:13).
Peace offerings were also called fellowship offerings. They expressed peace and fellowship between the person making the offering and the Lord.
Grain offerings. Grain was highly valued by nomads such as the Israelites, since it could not be grown in the desert. Grain offerings were thus an act of worship and thanksgiving.
Burnt offerings were the most costly type of sacrifice. Unlike other offerings, none of the remains could be used for other purposes.