Ramban on Numbers 32:19/רמב"ן על במדבר ל״ב:י״ט

1FOR OUR INHERITANCE HAS COME TO US — “we have already received it on the eastern side [of the Jordan].” This is Rashi’s language. But it would not be correct for them to speak in this manner in front of Moses, saying, “we have already received it,” for it was not up to them, but on his will that the matter depended, and they did not receive it until he [decided to] give it to them. Instead, [the explanation of their words is that] they said to Moses: “For you do not have to give us an inheritance with them, thereby making their inheritance in their good Land smaller, for an inheritance which is suitable for us has come to us, since it is a land [fit] for cattle, and we have more cattle than the other tribes.” This they said in the nature of a request, not by way of contention. Or perhaps they said: “For we will not inherit with them, because even if you do not want to give us the land [on the east side of the Jordan] now, we will cross over together with them [the rest of the children of Israel], we and all that we have, but we will not inherit with them, for we will return to this land which is the inheritance that is suitable for us, and which we want, and which none of the other tribes want at all.”