פירוש על יהושע 3:5

And Yehoshua said. This was on the third day, and the thirtieth day of mourning [for Moshe] was on the first of the three days.

הִתְקַדָשׁוּ usually means sanctify yourselves, but here it means prepare yourselves.

For tomorrow when you cross the Jordan.

Wonders. This translation follows that of Targum Yonasan.