Matthew 1:2

2. Begat Isaac His birth is given Genesis 21:2. Jacob Genesis 25:26. Judas and his brethren Genesis 29:0.

And his brethren At several points in the genealogy there are individual matters added, not forming an essential part of the lineage. Such are the clauses and his brethren in this verse; and Zara of Thamar in the third verse; of Rachab in the fifth verse; the king in the sixth verse; and of her that had been the wife of Urias in the same verse. Profound reasons have been sought for these additions, somewhat unnecessarily, by commentators. If we may suppose Matthew to have copied the home genealogy in the family of Joseph, these incidents may easily be supposed to have been freely inserted as interesting allusions to popular points or characters in Jewish sacred history. Certainly no genealogy of that day could have suggested more points of interesting reminiscence than that of this son of David, and putative father of the Messiah. The only difficulty is with the clause concerning Rachab, who, as some have thought, could not, upon chronological grounds, have been identical with the Rahab of Jericho, if she were the wife of Salmon.

But Alford well says; “Those very grounds completely tally with their identity. For Naashon (the father of Salmon) offered his offering at the setting up of the tabernacle (Numbers 7:12) thirty-nine years before the taking of Jericho. So that Salmon would be of mature age at or soon after that event; at which time Rahab was probably young, as her father and mother were living (Joshua 6:23.) Nor is it any objection that Achan, the fourth in descent from Judah by Zara, is contemporary with Salmon, the sixth of the other branch, since the generations in the line of Zara average sixty-nine years, and those in the line of Pharez forty-nine; both within the limits of probability. The difficulty of the interval of 366 years between Rahab and David does not belong to this passage only, but equally to Ruth 4:21-22; and is by no means insuperable, especially when the extreme old age of Jesse, implied in 1 Samuel 17:12, is considered.”