Charles Ellicott Commentary Exodus 30:21

"So they shall wash their hands and their feet, that they die not: and it shall be a statute for ever to them, even to him and to his seed throughout their generations." — Exodus 30:21 (ASV)

A statute for ever. —Compare Exodus 27:21; Exodus 28:43; Exodus 29:9. The external act was to continue so long as the dispensation lasted; the internal purity, which it symbolized, would be required of those who entered the Divine Presence for ever. (See Hebrews 12:14.)

THE COMPOSITION OF THE HOLY OIL.