According to their armies - צבאתם tsibotham, their battalions - regularly arranged troops. As God had these particularly under his care and direction, he had the name of צבאות יהוה Yehovah tsebaoth, Lord of hosts or armies. "The plain and disinterested manner," says Dr. Dodd, "in which Moses speaks here of his relations, and the impartiality wherewith he inserts in the list of them such as were afterwards severely punished by the Lord, are striking proofs of his modesty and sincerity. He inserts the genealogy of Reuben and Simeon, because they were of the same mother with Levi; and though he says nothing of himself, yet he relates particularly what concerns Aaron, Exodus 6:23, who married into an honorable family, the sister of a prince of the tribe of Judah."
This emphatic repetition shows the reason for inserting the genealogy. The names of Moses and Aaron are given twice and in a different order; used in Exodus 6:26 probably to mark Aaron as the older in the genealogy, and used in Exodus 6:27 to denote the leadership of Moses.