Now the sons of Reuben the firstborn of Israel, (for he was the firstborn; but, forasmuch as he defiled his father's bed, his birthright was given unto the sons of Joseph the son of Israel: and the genealogy is not to be reckoned after the birthright.
Sons of Israel — This is added emphatically, because they were treated as if they had been the immediate sons of Jacob.
Not reckoned — This is the second reason, which sheweth both why Reuben's genealogy was not first mentioned; and if another tribe was to be ranked before it, why that was Judah, and not Joseph, because the order of their genealogy was not to be ruled by the birthright, but by an higher privilege, which was given to Judah.
 For Judah prevailed above his brethren, and of him came the chief ruler; but the birthright was Joseph's:)
Judah — Not the person, but the tribe of Judah.
Prevailed — Excelled the other tribes, especially in the following privilege.
 And eastward he inhabited unto the entering in of the wilderness from the river Euphrates: because their cattle were multiplied in the land of Gilead.
Euphrates — From Jordan and the wilderness beyond it unto Euphrates. Or, of the wilderness, which lies towards or reacheth to the river Euphrates, namely, the great wilderness of Kedemoth, Deuteronomy 2:26, which was extended far and wide towards Euphrates: for that was the eastern border of Reuben's possession, and not Euphrates, to which their habitation never reached.
Multiplied — Which forced them to enlarge their habitation as far as they could towards Euphrates.
 And in the days of Saul they made war with the Hagarites, who fell by their hand: and they dwelt in their tents throughout all the east land of Gilead.
They made war — Thus God did for his people, as he promised them. He cast out the enemy from before them by little and little, and gave them their land as they had occasion for it.
 These are the children of Abihail the son of Huri, the son of Jaroah, the son of Gilead, the son of Michael, the son of Jeshishai, the son of Jahdo, the son of Buz;
These — These seven last named.
 And they were helped against them, and the Hagarites were delivered into their hand, and all that were with them: for they cried to God in the battle, and he was intreated of them; because they put their trust in him.
Helped — By God, verse 22, who gave them extraordinary courage and success.
 For there fell down many slain, because the war was of God. And they dwelt in their steads until the captivity.
Was of God — Undertaken in his fear, and carried on in a dependence on him. Then we may expect to prosper in any enterprize, and then only, when we take God along with us.