Yehoshua 4:21-23

And he spoke unto the Bnei Yisroel, saying, When your banim shall ask their avot in time to come, saying, What mean these avanim? Then ye shall let your banim know, saying, Yisroel crossed over this Yarden on yabashah (dry land). For Hashem Eloheichem dried up the waters of the Yarden from before you, until ye were passed over, just as Hashem Eloheichem did to Yam Suf, which He dried up from before us, until we were crossed over;