וְהוֹדַעְתֶּ֖ם אֶת־בְּנֵיכֶ֣ם לֵאמֹ֑ר בַּיַּבָּשָׁה֙ עָבַ֣ר יִשְׂרָאֵ֔ל אֶת־הַיַּרְדֵּ֖ן הַזֶּֽה׃
then ye shall let your children know, saying: Israel came over this Jordan on dry land.
Read Kabbalistic (mystical) interpretations of Joshua 4:22: Zohar and classical Jewish mystical sources, free online.