Numbers 32:21

Moses agreed to the terms offered by Reuben and Gad. If they helped their relatives fight the Canaanites, they would fulfill their part of the agreement. Then they could return to their settlements east of the Jordan River (32:22). If they did not keep their promise, it would be a serious sin against God (32:23).

Moses said unto them, If ye will do this thing--with sincerity and zeal.

go before the Lord to war--The phrase was used in allusion to the order of march in which the tribes of Reuben and Gad immediately preceded the ark (see on Num. 2:10-31), or to the passage over the Jordan, in which the ark stood in mid-channel, while all the tribes marched by in succession (Jos 3:4), of course including those of Reuben and Gad, so that, literally, they passed over before the Lord and before the rest of Israel (Jos 4:13). Perhaps, however, the phrase is used merely in a general sense to denote their marching on an expedition, the purpose of which was blessed with the presence, and destined to promote the glory, of God. The displeasure which Moses had felt on the first mention of their proposal had disappeared on the strength of their solemn assurances. But a lurking suspicion of their motives seems still to have been lingering in his mind--he continued to speak to them in an admonitory strain; and he concluded by warning them that in case of their failing to redeem their pledge, the judgments of an offended God would assuredly fall upon them. This emphatic caution against such an eventuality throws a strong doubt on the honesty of their first intentions; and yet, whether through the opposing attitude or the strong invectives of Moses they had been brought to a better state of mind, their final reply showed that now all was right.

And Moses said unto them. Moses might seem to err on the side of excessive good-nature, in that he extends the boundaries prescribed by God, in complying with their wish. For, since their inheritance had been promised them in the land of Canaan, they ought to have been contented with that as their abode; nor was it allowable for Moses to make any alteration in the Divine decree. There is also another thing no less inconsistent, that in a point of so much perplexity, Moses does not, as usual, consult God, but gives an immediate answer, which indirectly overthrows the previous ordinance of God. And, in truth, their desire was by no means excusable, since it would have never entered their minds, if they had borne in memory the covenant of God, and had been satisfied with this goodness: since it cannot be but that the flesh should be constantly running riot, unless kept under restraint by the calling of God. But God, who knows how to bring light out of darkness, not only pardoned their error, but takes occasion also to extend His liberality. Thus the land of Bashan, and its neighborhood, were added to the former boundaries. At the same time, however, He shewed on the other hand how much better it would have been for them to have been kept together, so that they might have mutually protected each other, and dwelt securely in their appointed habitation. And, after the lapse of a long period, the Reubenites and Gadites learnt from experience that they had been too hasty in wishing for the land which they obtained; nevertheless, through God's indulgence, that which might justly have been injurious to them, turned out for their advantage.

We may gather, however, from the result, that Moses was guilty of no rashness in his interference with the ordinance, of God, both because he commands that which he now determines to be ratified and maintained after his death; and when, in the book of Joshua, it is recorded that the several tribes had their inheritance assigned to them, this country beyond Jordan is excepted, as having been granted by Moses to the tribes of Reuben and Gad and half of Manasseh. Hence it is evident that his decision was approved by God. Moreover, since he is there often honored with the title of "servant of God," we are taught that nothing was done by him in this matter without the authority of God, and the guidance of His Spirit. Neither is it at random that he here so often makes use of God's name, but rather does he thus imply that whatever he does is suggested by Him.

And will go all of you armed over Jordan before the Lord,.... Moses tries them thoroughly, and is very express in his words, requiring them not only to go armed, or march from the place where they were, towards the land of Canaan, but to go over Jordan, and not some of them only, but all, and that before the Lord; though indeed, when the tribes came to the river Jordan, the ark, which was the symbol of the divine Presence, went before all the tribes into it, and there stayed till they passed over, and then these two tribes and the half tribe of Manasseh passed before the children of Israel, and before the Lord, unto battle, Joshua 3:11.

until he hath driven out his enemies before him: the Canaanites, who were the enemies of the Lord, as well as of his people; and because of their sins, in which they showed their enmity to God, the land spewed them out, and he drove them out to make way for his people Israel, and till this was done the tribes of Reuben and Gad were to continue with them.

Upon this declaration Moses absolves them from all guilt, and promises them the desired land for a possession, on condition that they fulfil their promise; but he reminds them again of the sin that they will commit, and will have to atone for, if their promise is not fulfilled, and closes with the admonition to build towns for their families and pens for their flocks, and to do what they have promised. Upon this they promise again (Num 32:25-27), through their spokesman (as the singular ויּאמר in Num 32:25, and the suffix in אדני in Num 32:27, clearly show), that they will fulfil his command. The use of the expression "before Jehovah," in the words, "go armed before Jehovah to war," in Num 32:20 and Num 32:21, may be explained from the fact, that in the war which they waged at the command of their God, the Israelites were the army of Jehovah, with Jehovah in the midst. Hence the ark of the covenant was taken into the war, as the vehicle and substratum of the presence of Jehovah; whereas it remained behind in the camp, when the people wanted to press forward into Canaan of their own accord (Num 14:44). But if this is the meaning of the expression "before Jehovah," we may easily understand why the Reubenites and Gadites do not make use of it in Num 32:17, namely, because they only promise to go equipped "before the children of Israel," i.e., to help their brethren to conquer Canaan. In Num 32:32 they also adopt the expression, after hearing it from the mouth of Moses (Num 32:20).
(Note: This completely sets aside the supposed discrepancy which Knobel adduces in support of his fragmentary hypothesis, viz., that the Elohist writes "before Israel" in Num 32:17 and Num 32:29, when the Jehovist would write "before Jehovah," - a statement which is not even correct; since we find "before Jehovah" in Num 32:29, which Knobel is obliged to erase from the text in order to establish his assertion.)
נקיּים, innocent, "free from guilt before Jehovah and before Israel." By drawing back from participation in the war against the Canaanites, they would not only sin against Jehovah, who had promised Canaan to all Israel, and commanded them to take it, but also against Israel itself, i.e., against the rest of the tribes, as is more fully stated in Num 32:7-15. In Num 32:22, "before Jehovah" signifies according to the judgment of Jehovah, with divine approval. חטּאתכם וּדעוּ, "ye will know your sin," which will overtake (מצא) or smite you, i.e., ye will have to make atonement for them.