Exodus 19:10 - Matthew Poole's English Annotations on the Holy Bible

i.e. Command them to sanctify and cleanse themselves from all filthiness of flesh and spirit, and to prepare their hearts for the right receiving of my laws, and solemn entering into covenant with me. Compare Leviticus 11:45 Joshua 3:5, Joshua 7:13. Let them wash their clothes; by which external washing, which was agreeable to that state of the church, they were taught to cleanse their inward man.