Go unto the people, and sanctify them. — The approaching manifestation required, above all things, that the people should be “sanctified.” Sanctification is twofold — outward and inward. The real essential preparation for approach to God is inward sanctification; but no external command can secure this. Moses was therefore instructed to issue directions for outward purification; and it was left to the spiritual insight of the people to perceive and recognise that such purity symbolised and required internal purification as its counterpart. The external purification was to consist in three things — (1) Ablution, or washing of the person; (2) washing of clothes; and (3) abstinence from sexual intercourse (Exodus 19:15).
Let them wash their clothes. — The Levitical law required the washing of clothes on many occasions (Leviticus 11:25; Leviticus 11:28; Leviticus 11:40; Leviticus 13:6; Leviticus 13:34; Leviticus 13:58; Leviticus 14:8-9; Leviticus 14:47; Leviticus 15:5-22, &c.) In connection with purification. The same idea prevailed in Egypt (Herod., 2:37), in Greece (Horn. Od., iv. 1. 759), and in Rome (Dollinger, Jew and Gentile, vol. ii., p. 82). It is a natural extension of the idea that ablution of the person cleanses, not from physical only, but from moral defilement.