And they answered Joshua, saying, All that thou hast commanded us we will do, and whithersoever thou sendest us we will go.
Joshua recalled the condition Moses had set when he granted them the eastern land: they must fulfill their oath to fight. The word "all" should not be pressed, only about 40,000 of the 110,000 fighting men crossed Jordan; the rest remained to defend their families, flocks, and territory they had taken.
AI summary
Commenting on Joshua 1:12-18
And they answered Joshua,.... The two tribes of Gad and Reuben, and the half tribe of Manasseh, the heads of them, such as were deputed for that purpose, and were their mouths to him: saying, all that thou commandest we will do; with respect to this affair of going over Jordan with their brethren, to assist them in the conquest of the land of Canaan...
16. And they answered, etc They not only acquiesce, but freely admit and explicitly detail the obedience which they owe. Our obligations are duly discharged only when we perform them cheerfully, and not in sadness, as Paul expresses it. (2 Corinthians 9:7.) If it is objected that there is little modesty in their boast of having been obedient to Moses whom they had often contradicted...