'Purify Yourselves' in the Bible

Then Jacob said to his household and to all who were with him, “Get rid of the [idols and images of] foreign gods that are among you, and ceremonially purify yourselves and change [into fresh] clothes;

Camp outside the camp for seven days; whoever has killed any person and whoever has touched any dead body, purify yourselves and your captives, on the third day and on the seventh day.