Numbers 32:27

Reuben and Gad kept their promise (Joshua 4:12–13; 22:1–9).

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.

But if ye will not do so. He makes a solemn protestation that they will deal wickedly, if they break their promise: and at the same time denounces punishment against them, as if he were summoning them before the tribunal of God. But, although he speaks conditionally of that particular engagement, whereby the two tribes had voluntarily bound themselves, still we may derive from his words the general doctrine, that, unless we abide by our promises, God will always be the avenger of fraud and treachery. The expression, "Sin will find you out," is more emphatic than as if he had simply said, You shall not escape God's hand; for the meaning of it is that vengeance is so connected with sin, that it cannot be severed from it. Thus, in Genesis 4:7, it is said, "Sin lieth at the door," to lay hold at length of the guilty. For, such is our propensity to sin, that we too often find from experience that we are encouraged to audacity by God's forbearance, whilst we think that we have escaped, if He makes as though He saw us not for a time.

But thy servants will pass over,.... The river Jordan, and go into the land of Canaan:

every man armed for war; Moses had required that all should go over, and they consent to it, and promise that everyone should, though this was not insisted on when they came to it, for only about 40,000 went over, Joshua 4:13, whereas the two tribes of Gad and Reuben, and the half tribe of Manasseh, numbered more than 110,000; see Numbers 26:7,

before the Lord to battle, as my lord saith; for now, instead of saying, "before the children of Israel", a phrase they first used, they say, "before the Lord", as Moses had expressed it.

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.