Now the children of Reuben and the children of Gad had a very great multitude of cattle: and when they saw the land of Jazer, and the land of Gilead, that, behold, the place was a place for cattle;
Jazer — A city and country of the Amorites; Gilead - A mountainous country, famous for pasturage
 And Moses said unto the children of Gad and to the children of Reuben, Shall your brethren go to war, and shall ye sit here?
Ye sit here — In ease and peace, while your brethren are engaged in a bloody war.
 Save Caleb the son of Jephunneh the Kenezite, and Joshua the son of Nun: for they have wholly followed the LORD.
The Kenezite — So called from Kenaz, his grand-father.
 For if ye turn away from after him, he will yet again leave them in the wilderness; and ye shall destroy all this people.
All this people — Who being moved by your counsel and example, will refuse to go over Jordan.
 But we ourselves will go ready armed before the children of Israel, until we have brought them unto their place: and our little ones shall dwell in the fenced cities because of the inhabitants of the land.
We ourselves — Either all, or as many as shall be thought necessary, leaving only so many as may be necessary to provide for the sustenance and defence of our wives and children here.
 And Moses said unto them, If ye will do this thing, if ye will go armed before the LORD to war,
Before the Lord — Before the ark, which was the token of God's presence. He alludes either to the order of the tribes in their march, whereby Reuben and Gad marched immediately before the ark, or to the manner of their passage over Jordan, wherein the ark went first into Jordan, and stood there while all the tribes marched over Jordan by and before it, and these amongst the rest, as is expressly noted in these very words, that they passed over before the Lord, Joshua 4:13.
 And the land be subdued before the LORD: then afterward ye shall return, and be guiltless before the LORD, and before Israel; and this land shall be your possession before the LORD.
Before the Lord — By his presence and gracious and powerful assistance.
 But if ye will not do so, behold, ye have sinned against the LORD: and be sure your sin will find you out.
Your sin — The punishment of your sin. Sin will certainly find out the sinner sooner or later. It concerns us therefore to find our sins out, that we may repent of them and forsake them, lest our sins find us out, to our confusion and destruction.
 But if they will not pass over with you armed, they shall have possessions among you in the land of Canaan.
They shall have possession — They shall forfeit their possessions in Gilead, and be constrained to go over Jordan, and to seek possessions there among their brethren.
 And the children of Gad and the children of Reuben answered, saying, As the LORD hath said unto thy servants, so will we do.
As the Lord hath said — Either at this time by thy mouth: or formerly, where he commanded us, as well as our brethren to go into Canaan and possess it.
 And the children of Gad built Dibon, and Ataroth, and Aroer,
Built — Repaired and fortified. For they neither had need nor leisure as yet to do more, the old cities not being burnt and ruined, as divers in Canaan were.
 And Nebo, and Baalmeon, (their names being changed,) and Shibmah: and gave other names unto the cities which they builded.
Their names changed — Either because conquerers of places used to do so: or because the names of other Gods (which Nebo and Baal-meon unquestionably were) were not to be mentioned, Exodus 23:13.
 And Moses gave Gilead unto Machir the son of Manasseh; and he dwelt therein.
Machir — Not to Machir himself, who doubtless was long since dead, but the family or posterity of Machir.
 And Nobah went and took Kenath, and the villages thereof, and called it Nobah, after his own name.
Nobah — Who, though not else where named, was doubtless an eminent person of the tribe of Manasseh. 'Tis observable, that these tribes, as they were placed before the other tribes, so they were displaced before them. They were carried captive by the king of Assyria, some years before the other tribes. Such a proportion does providence frequently observe, in balancing prosperity and adversity.