Go unto the people. Moses had withdrawn himself from the people to report their words to God (Exodus 19:8, Exodus 19:9). He was now commanded to return to them. Sanctify them. Or "purify them." Purification in Egypt was partly by washing, partly, by shaving the hair, either front the head only, or from the entire body (Herod.
2.37), partly perhaps by other rites. The Israelites seem ordinarily to have purified themselves by washing only. To-day and to-morrow. The fourth and fifth of Sivan, according to the Jewish tradition, the Decalogue having been given upon the sixth.
The requirement of a two-days' preparation marked the extreme sanctity of the occasion. Let them wash their clothes. Compare Le Exodus 15:5. Rich people could "change their garments" on a sacred occasion (Genesis 35:2); the poorer sort, having no change, could only wash them.