But if they will not pass over with you armed: Moses summarizes the conditions in the previous verse to introduce how the Gadites and Reubenites will be punished if they do not fulfil them (compare verse 23). Translators may begin a new sentence here.

They shall have possessions among you in the land of Canaan: This clause specifies the punishment. If the Gadites and Reubenites fail to keep the covenant, their request for land east of the Jordan will be denied (so Ashley, page 614). Instead, they will receive land in Canaan with the other tribes. In many languages Revised Standard Version‘s literal rendering of this clause will not sound like a punishment. If so, the following models may be helpful: “they must accept their possession with you in Canaan” (New International Version), “then they must accept land with the rest of you in the land of Canaan” (New Living Translation; similarly Nueva Traducción Viviente), and “then they must content themselves with a piece of [left-over] land among you [in Canaan]” (Die Bibel im heutigen Deutsch).

Quoted with permission from de Regt, Lénart J. and Wendland, Ernst R. A Handbook on Numbers. (UBS Helps for Translators). Miami: UBS, 2016. For this and other handbooks for translators see here .