He that is armed, or rather disencumbered, i.e; prepared for battle (see Joshua 4:13). Similarly, in the next verse, "the armed men," i.e; the host in marching order, as we say. Kimchi and Jarchi refer this to the Reubenites and their brethren, but without sufficient authority.
Keil thinks that it was impossible that the unarmed people would have gone with the procession as "the rereward" (see note on Joshua 5:13), because no command to that effect is given in Joshua 6:3. But as he has told us in Joshua 3:1-17; Joshua 4:1-24; and as we have just seen in Joshua 4:4.
the command to Joshua is not fully given. A short abstract of it is given, and it is to be filled up in detail from the subsequent narrative.