Exodus 29:7

29:7 You are to take the anointing oil and pour it on his head and anoint him. ¹ 

Exodus 29:21

29:21 You are to take some of the blood that is on the altar and some of the anointing oil and sprinkle it ²  on Aaron, on his garments, on his sons, and on his sons’ garments with him, so that he may be holy, ³  he and his garments along with his sons and his sons’ garments.

[29:7]  ¹ sn The act of anointing was meant to set him apart for this holy service within the house of Yahweh. The psalms indicate that no oil was spared in this ritual, for it ran down his beard and to the hem of his garment. Oil of anointing was used for all major offices (giving the label with the passive adjective “mashiah” (or “messiah”) to anyone anointed. In the further revelation of Scripture, the oil came to signify the enablement as well as the setting apart, and often the Holy Spirit came on the person at the anointing with oil. The olive oil was a symbol of the Spirit in the OT as well (Zech 4:4-6). And in the NT “anointing” signifies empowerment by the Holy Spirit for service.

[29:21]  ² tn Here “it” has been supplied.

[29:21]  ³ tn The verb in this instance is Qal and not Piel, “to be holy” rather than “sanctify.” The result of all this ritual is that Aaron and his sons will be set aside and distinct in their life and their service.