Aaron’s sons: Moses was from the tribe of Levi. This tribe divided into two groups:
priests, who were descendants of Aaron, the first high priest; and
Levites, who served in supporting roles (Exodus 28:1–4; Numbers 18:1–7).
These instructions also applied to future generations.
the blood: This symbolized life, not death. The basis of the Israelite sacrifice system was substitution. Shedding sacrificial blood was essential for atonement. It meant sacrificing the animal's life as a substitute for the worshiper's life (Leviticus 17:10–14; Hebrews 9:22). Jesus Christ's shed his blood as the ultimate sacrifice for sin (Hebrews 9:11–14).
the altar of burnt offering was at the east end of the courtyard. It was outside the Tent of Meeting but inside the courtyard entrance (Exodus 40:6, 29).