Joshua 4:10-13 NIV

10 Now the priests who carried the ark remained standing in the middle of the Jordan until everything the LORD had commanded Joshua was done by the people, just as Moses had directed Joshua. The people hurried over,
11 and as soon as all of them had crossed, the ark of the LORD and the priests came to the other side while the people watched.
12 The men of Reuben,1 Gad2 and the half-tribe of Manasseh3 crossed over, armed, in front of the Israelites,4 as Moses had directed them.5

References for Joshua 4:12

13 About forty thousand armed for battle6 crossed over7 before the LORD to the plains of Jericho for war.

References for Joshua 4:13