Observe here, 1. That only the names of Esau's sons and grandsons are recorded, only their names, not their history; for it is the church that Moses preserves the records of, not the record of those that are without. Those elders that lived by faith alone obtained a good report. It is Sion that produces men of renown, not Seir, Psa 87:5. Nor does the genealogy go any further than the third and fourth generation; the very names of all after are buried in oblivion. It is only the pedigree of the Israelites, who were to be the heirs of Canaan, and of whom were to come the promised seed, and the holy seed, that is drawn out to any length, as far as there was occasion for it, even of all the tribes till Canaan was divided among them, and of the royal line till Christ came. 2. That these sons and grandsons of Esau are called dukes, Gen 36:15-19. Probably they were military commanders, dukes, or captains, that had soldiers under them; for Esau and his family lived by the sword, Gen 27:40. Note, Titles of honour have been more ancient out of the church than in it. Esau's sons were dukes when Jacob's sons were but plain shepherds, Gen 47:3. This is not a reason why such titles should not be used among Christians; but it is a reason why men should not overvalue themselves, or others, for the sake of them. There is an honour that comes from God, and a name in his house that is infinitely more valuable. Edomites may be dukes with men, but Israelites indeed are made to our God kings and priests. 3. We may suppose those dukes had numerous families of children and servants that were their dukedoms. God promised to multiply Jacob, and to enrich him; yet Esau increases, and is enriched first. Note, It is no new thing for the men of this world to be full of children, and to have their bellies too filled with hidden treasures, Psa 17:14. God's promise to Jacob began to work late, but the effect of it remained longer, and it had its complete accomplishment in the spiritual Israel.

Dukes of the sons of Esau - The word duke comes from the Latin dux, a captain or leader. The Hebrew אלוף alluph has the same signification; and as it is also the term for a thousand, which is a grand capital or leading number, probably the אלופי alluphey or dukes had this name from being leaders of or captains over a company of one thousand men; just as those among the Greeks called chiliarchs, which signifies the same; and as the Romans called those centurions who were captains over one hundred men, from the Latin word centum, which signifies a hundred. The ducal government was that which prevailed first among the Idumeans, or descendants of Esau. Here fourteen dukes are reckoned to Esau, seven that came of his wife, Adah, four of Bashemath, and three of Aholibamah.

And these are the sons of Reuel.... See Gill on Gen 36:15.
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Genesis 36:18

gen 36:18
gen 36:18
gen 36:18And these are the sons of Aholibamah Esua's wife;.... See Gill on Gen 36:15.

dukes--The Edomites, like the Israelites, were divided into tribes, which took their names from his sons. The head of each tribe was called by a term which in our version is rendered "duke"--not of the high rank and wealth of a British peer, but like the sheiks or emirs of the modern East, or the chieftains of highland clans. Fourteen are mentioned who flourished contemporaneously.