Numbers 32:20-22

20And Moses said to them, If ye do this thing, if ye arm yourselves before Jehovah for war,

21and all of you that are armed go over the Jordan before Jehovah, until he have dispossessed his enemies from before him,

22and the land is subdued before Jehovah, and afterwards ye return, ye shall be guiltless toward Jehovah and toward Israel, and this land shall be your possession before Jehovah.