וַיֹּ֨אמֶר יְהוָ֤ה אֶל־מֹשֶׁה֙ לֵ֣ךְ אֶל־הָעָ֔ם וְקִדַּשְׁתָּ֥ם הַיּ֖וֹם וּמָחָ֑ר וְכִבְּס֖וּ שִׂמְלֹתָֽם׃
여호와께서 모세에게 이르시되 너는 백성에게로 가서 오늘과 내일 그들을 성결케 하며 그들로 옷을 빨고
Mishneh Torah, Forbidden Intercourse
Immersion was in the desert before receiving the Torah, as is said, "Sanctify yourselves today and tomorrow; wash your clothes." The offering, as is said, "Send the young ones of Israel to bring elevation offerings" - and everyone in Israel brought them.