וְכִבַּסְתֶּ֧ם בִּגְדֵיכֶ֛ם בַּיּ֥וֹם הַשְּׁבִיעִ֖י וּטְהַרְתֶּ֑ם וְאַחַ֖ר תָּבֹ֥אוּ אֶל־הַֽמַּחֲנֶֽה׃ (פ)
And ye shall wash your clothes on the seventh day, and ye shall be clean, and afterward ye may come into the camp.’
Read kabbalistic (mystical) interpretation of Numbers 31:24: and classical mystical sources.