Here, the word sanctify does not mean "set apart" but "consecrate" or "dedicate" or "make pure." The word holy has two meanings: "to set aside" and "to set apart" or "to cut out." However, it always carries a sense of "purity."
Notice what Moses is told to do: ". . . and let them wash their clothes." In the New Testament, clean, washed clothes symbolize the righteous acts of the saints. In this instance, they physically had to wash their clothes—to purify them. What were the people about to do? In a short time, they were going to draw near to God. And in order to draw near to God, they had to be clothed—encompassed—by righteous acts.
