Numbers 19:3

Of all. Hebrew, "before his face." Septuagint, "they shall bring her out, slay and burn her before him," which must be referred to some other priests, who accompanied Eleazar on this occasion, ver. 8. (Calmet)

Aaron did not perform this office, as the sacrifice was not solemn, but sorrowful, and designed for purification. (Menochius)

The Rabbins say, however, that the high priest performed this ceremony ever after; and, since the building of the temple, they did it upon Mount Olivet. This is also remarked by St. Jerome, ep. 27. It was thus a more lively figure of Jesus Christ sweating blood on that same ground; as the smoke might represent his ascension, Acts i. 10., and Luke xxii. 44. (Calmet)

He died out of Jerusalem, in full age, (ver. 2,) or 33 years old, being wounded in every part for our transgressions, (ver. 5,) setting us an example how to suffer, (ver. 6,) and by his blood communicating virtue to the sacraments, ver. 5. His body, derived from Adam, (or red earth, ver. 2,) was buried in a most clean place, (ver. 9,) and those who crucified him became more unclean; (ver. 8,) while even those who were employed in burying him, (ver. 9,) required to be cleansed by the grace of his passion, which must be communicated to them by baptism, in the name of the blessed Trinity, without which they cannot partake of any of the sacraments, chap. xii. The old law could bring nothing to perfection. Those who lived under that dispensation, were forced to wait till the evening, (ver. 7,) when in the last ages the new law commenced, that by faith in Christ, they might obtain the remission of their sins. Thus we perceive the meaning of many things which to the Jews were veiled in shadows, Hebrews x. (St. Augustine, q. 33.; Theodoret, q. 36.) (Worthington)