Upon completion of the tabernacle, God spoke to Moses and gave him instructions for a series of offerings that were to be made by the people. He was specific and precise in His requirements for those offerings. One can see through a study of the New Testament how these offerings were forerunners of the ultimate sacrifice that Christ made for man.
Of the twelve tribes of Israel, the tribe of Levi was selected as the priestly tribe. Aaron and his sons were chosen as high priest and priests with the remainder of the tribe being assistants (teachers, scribes and other types of ministers) to the priests.
These priests were to administer the offerings brought by the Israelites. By being fully occupied by the duties of the priesthood, they had no means of producing for their own needs. It was the responsibility of the other tribes to care for the necessities of the Levites.
The burnt offering was a free will sacrifice brought as atonement for their sins. It could be from the herd, flock or birds. If the offering was from the herd or flock, it must be a male without blemish. Birds were to be young. God expected the best from the Israelites. Likewise, He expects the best from us today.
As a grain offering, meal, cakes or firstfruits heads of grain could be brought to the priests. No leaven or honey was to be involved in the preparation of these sacrifices. Salt, however, was required as its seasoning.
The third offering required by God was a peace offering. This sacrifice could be a male or female from the herd or flock. As with the burnt offering, those animals were to be without blemish.