Exodus 19:10
And the LORD said unto Moses, Go unto the people, and sanctify them to day and to morrow, and let them wash their clothes,
And the Lord said unto Moses,.... On the fourth day, according to the Targum of Jonathan;
Go unto the people; go down from the mountain, from the top of it, where he now was, to the camp of Israel, which was pitched before it:
and sanctify them today and tomorrow; the fourth and fifth days of the month; that is, he was, to instruct them how they were to sanctify themselves in an external way, by washing themselves, as after mentioned, their bodies and clothes, and by abstaining from all sensual pleasures, lawful or unlawful:
and let them wash their clothes; which the Jews understood not of their garments, but of their bodies also; teaching them by these outward things the necessity of internal purity and holiness, to appear before God: these outward rites were in use before the law of Moses, as appears from Genesis 35:2 and the Heathens themselves have similar notions of the cleanness of bodies and garments, as well as the purity of mind, being acceptable to their deities {n}.
{n} "Casta placent superis, pura cum veste venito". Tibullus.