The condition proposed by the two and a half tribes of Reuvein, Gad and half of Menashe made with Moshe Rabbeinu, was met with resistance. Initially, Moshe was very upset with what he had heard.
When these tribes suggested remaining on the other side of the Jordan River, Moshe said the following: האחיכם יבואו למלחמה ואתם תשבו פה? "Will your brothers go off to battle, and you will remain here?" This is a very powerful Pasuk in two ways.
Moshe is concerned that that such action by these tribes will demoralize the nation. The pain of the report of the spies and what it did to the Jewish people was fresh in Moshe's mind.
And secondly, this is a Pasuk that cries out for the ages. Jews from all over the world must know that they must not sit back and let other Jews do their work for them. This certainly applies today with the Jews living in Eretz Yisrael and with the IDF defending Jews all over the world. They are doing their share in bringing honor and pride to our people. But those that shy away from their responsibility, would do well to listen to Moshe Rabbeinu's admonishment. "Shall your brothers go off to battle and you remain here?"