According as we listened to Moses in all things, so will we listen to you: only Yahweh your God be with you, as he was with Moses.
The big point of this whole paragraph  (Joshua 1:12-18) looks back to that urgent request made of Moses by the two and one half tribes that he would allot them their inheritance east of Jordan, and to the consequent promise which they made to Moses that they would aid their brethren in the conquest of the rest of Canaan.  That promise came due right here; and when Joshua confronted the trans-Jordanic group with their obligation, they accepted it.  Of course, the hardship and the struggle had not at that time begun.  "Obedience is easy when all goes well with us, and when it makes no demand upon our faith."[22]  It does not appear that those trans-Jordanic tribes fully lived up to their promises.  (See a full discussion of this in Vol. 3 of my commentary (Leviticus and Numbers) at  Numbers 32.)