This contradiction is rooted in variant textual traditions that were brought together during the Torah’s redaction. Not surprisingly, the only tradition that claims that these Transjordanian possessions will be assigned to the children of Reuben and Gad by Eleazar and Joshua after the conquest of Canaan is also the same tradition that assigns conditions to the granting of these possessions, which were discussed in the previous entry (#322)—the Priestly source.
So the conditions that were assigned in verse 23 (“if you won’t do this”) and verse 30 (“if they will not cross”) necessitate the granting of these Transjordanian possessions after these conditions have successfully been met, and thus after the conqest of Canaan. Thus, “this land will become yours” (v. 22) only if you crossover armed, and Eleazar and Joshua “shall give them the land” (v. 29) only if they crossover.
But in every other tradition—the earlier Yahwist and Deuteronomic—Moses is presented giving this land to the Reubenites and Gadites on the spot, when they request it or conquer it (see #317-318), before the conquest of Canaan.
And Moses gave them, the children of Gad and the children of Reuben and the half tribe if Manasseh son of Joseph, the kingdom of Sihon, king of the Amorites and the kingdom of Og, king of Bashan, the land with its cities, with the borders of the land all around. (Num 32:33)
And we took possession of this land at that time. I gave the Reubenites and the Gadites from Aroer, which is on the Wadi Arnon, and half of the hill country of Gilead and its cities. And I gave the rest of Gilead and all of Bashan, Og’s kingdom, to half the tribe of Manasseh. (Deut 3:12-13)
These traditions speak against the Priestly tradition, where the granting of these territories doesn’t happen till after the conquest!