This is an example of a synecdoche—a part representing the whole. The righthand side was considered the more important and favoured side (e.g., Genesis 48:17–20; Matthew 25:34, Matthew 25:41). Smearing blood on these body parts communicates that the priest belongs, in his entirety, to the service of the Lord. One commentator emphasizes the meaning of this by saying, “The priest must have consecrated ears ever to listen to God's holy voice; consecrated hands at all times to do holy deeds; and consecrated feet to walk evermore in holy ways” (Dillamann in Wenham p.143).
23 Moïse égorgea le bélier, prit de son sang, et en mit sur le lobe de l'oreille droite d'Aaron, sur le pouce de sa main droite et sur le gros orteil de son pied droit.