Priest: The Time of Moses: Hereditary, Descent of office
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Exodus 27:21
In the Tent of Meeting, outside the veil that is in front of the Testimony, Aaron and his sons are to tend the lamps before the LORD from evening until morning. This is to be a permanent statute for the Israelites for the generations to come.
Exodus 28:43
Aaron and his sons must wear them whenever they enter the Tent of Meeting or approach the altar to minister in the Holy Place, so that they will not incur guilt and die. This is to be a permanent statute for Aaron and his descendants.
Exodus 29:9
Wrap the sashes around Aaron and his sons and tie headbands on them. The priesthood shall be theirs by a permanent statute. In this way you are to ordain Aaron and his sons.