וַיֹּ֧אמֶר יְהוֹשֻׁ֛עַ אֶל־הָעָ֖ם הִתְקַדָּ֑שׁוּ כִּ֣י מָחָ֗ר יַעֲשֶׂ֧ה יְהוָ֛ה בְּקִרְבְּכֶ֖ם נִפְלָאֽוֹת׃
And Joshua said unto the people: ‘Sanctify yourselves; for to-morrow the LORD will do wonders among you.’
Read midrashic interpretation of Joshua 3:5: and classical rabbinic exegesis.