1 Now the children of Reuben and the children of Gad had a very great multitude of cattle. And when they saw the land of Jazer and the land of Gilead, that behold, the place was a place for cattle, 2 The children of Gad and the children of Reuben came and spoke to Moses, to Eleazar the priest, and to the princes of the congregation, saying, 3 "Ataroth, Dibon, Jazer, Nimrah, Heshbon, Elealeh, Shebam, Nebo, and Beon, 4 Even the country which the LORD smote before the congregation of Israel, is a land for cattle, and your servants have cattle. 5 Therefore," they said, "if we have found grace in your sight, let this land be given to your servants for a possession, and do not bring us over the Jordan."
6 And Moses said to the children of Gad and to the children of Reuben, "Shall your brothers go to war and shall you sit here? 7 And why do you discourage the heart of the children of Israel from going over into the land which the LORD has given them? 8 Thus your fathers did when I sent them from Kadesh-barnea to see the land. 9 For when they went up to the valley of Eshcol and saw the land, they discouraged the heart of the children of Israel so that they should not go into the land which the LORD had given them. 10 And the LORD'S anger was kindled the same time and he swore, saying, 11 'Surely none of the men who came up from Egypt, from twenty years old and upward, shall see the land which I swore to Abraham, to Isaac, and to Jacob, because they have not wholly followed me, 12 Except Caleb the son of Jephunneh the Kenezite and Joshua the son of Nun, for they have wholly followed the LORD.' 13 And the LORD'S anger was kindled against Israel and he made them wander in the wilderness forty years until all the generation who had done evil in the sight of the LORD was consumed. 14 And behold, you have risen up in your fathers' stead, an increase of sinful men, to augment yet the fierce anger of the LORD toward Israel. 15 For if you turn away from after him, he will yet again leave them in the wilderness and he will destroy all this people."
16 And they came near to him and said, "We will build sheep-folds here for our cattle and cities for our little ones, 17 But we ourselves will go armed ready before the children of Israel until we have brought them to their place. And our little ones shall dwell in the fortified cities because of the inhabitants of the land. 18 We will not return to our houses until the children of Israel have each inherited his inheritance. 19 For we will not inherit with them on the other side of the Jordan, or forward, because our inheritance has fallen to us on this side of the Jordan eastward."
20 And Moses said to them, "If you will do this thing, if you will go armed before the LORD to war, 21 And all of you will go armed over the Jordan before the LORD until he has driven out his enemies from before him, 22 And the land is subdued before the LORD, then afterward you shall return and be guiltless before the LORD and before Israel. And this land shall be your possession before the LORD. 23 But if you will not do so, behold, you have sinned against the LORD. And be sure your sin will find you out. 24 Build yourselves cities for your little ones and folds for your sheep, and do that which has proceeded out of your mouth."
25 And the children of Gad and the children of Reuben spoke to Moses, saying, "Your servants will do as my lord commands. 26 Our little ones, our wives, our flocks, and all our cattle shall be there in the cities of Gilead, 27 But your servants will pass over, every man armed for war, before the LORD to battle, as my lord says."
28 So concerning them Moses commanded Eleazar the priest, Joshua the son of Nun, and the chief fathers of the tribes of the children of Israel, 29 And Moses said to them, "If the children of Gad and the children of Reuben will pass with you over the Jordan, every man armed for battle, before the LORD, and the land is subdued before you, then you shall give them the land of Gilead for a possession. 30 But if they will not pass over with you armed, they shall have possessions among you in the land of Canaan." 31 And the children of Gad and the children of Reuben answered, saying, "As the LORD has said to your servants, so we will do. 32 We will pass over armed before the LORD into the land of Canaan so that the possession of our inheritance on this side of the Jordan may be ours."
33 And Moses gave to them, even to the children of Gad, to the children of Reuben, and to half the tribe of Manasseh the son of Joseph, the kingdom of Sihon king of the Amorites and the kingdom of Og king of Bashan, the land with its cities in the borders, even the cities of the country around. 34 And the children of Gad built Dibon, Ataroth, Aroer, 35 Atroth, Shophan, Jaazer, Jogbehah, 36 Beth-nimrah, and Beth-haran—fortified cities—and folds for sheep. 37 And the children of Reuben built Heshbon, Elealeh, Kirjathaim, 38 Nebo, Baal-meon (their names being changed), and Shibmah, and gave other names to the cities which they built. 39 And the children of Machir the son of Manasseh went to Gilead and took it and dispossessed the Amorite who was in it. 40 And Moses gave Gilead to Machir the son of Manasseh, and he dwelt in it. 41 And Jair the son of Manasseh went and took its small towns and called them Havoth-jair. 42 And Nobah went and took Kenath and its villages and called it Nobah after his own name.
[v.29] - The children of Gad and Reuben fulfilled their promise and were given possession of the land they desired. Reference, Joshua 22:1-6.