In Matthew 1:5 it appears that there are only 4 generations from Rahab to David. This doesn't seem possible. I thought that period would have been 300-400 years (Judges). Am I missing something?
First, the use of "father of" or "son of" can refer to any descendent. E.g. the claim that "Abraham is our father" in Matt 3.9. The pharisees did not say this because they were confused about who their own fathers were, or because they thought they were all biological brothers, but rather they were making a claim to be inheritors of the promise given to Abraham. In the ancient world, saying that you were "a son of someone" was equivalent to making a specific set of claims about inheritance, and saying that you were a "father of" merely meant that this person was your descendent.
That we know only selected ancestors were included is clear, for example from the seven kings listed verses 8-9: and Joram became the father of Uzziah
we see that three kings are skipped: Ahaziah, Joash, and Amaziah
nevertheless Joram was the father of Uzziah through these kings, but there was no claim on Christ inheriting anything from these three.
David's geneology in Ruth and Chronicles
Now the portion of Matthew's geneology from Perez to David is taken from the book of Ruth, so this question is not about Matthew, but about Ruth:
Perez fathered Hezron,
and Hezron fathered Ram,
and Ram fathered Amminadab,
and Amminadab fathered Nahshon,
and Nahshon fathered Salmon,
**and Salmon (also Salma) fathered Boaz,
and Boaz fathered Obed,
and Obed fathered Jesse,
and Jesse fathered David.** Ruth 4.18-22
We have the same geneology in first chronicles 2.5-15:
The sons of Perez: Hezron and Hamul.
The sons of Hezron who were born to him: Jerahmeel, Ram, and Caleb.
And Ram fathered Amminadab, and Amminadab fathered Nahshon, prince of the sons of Judah.
And Nahshon fathered Salma, and Salma fathered Boaz.
And Boaz fathered Obed, and Obed fathered Jesse.
And Jesse fathered Eliab his firstborn, Abinadab the second, Shimea the third, Nethanel the fourth, Raddai the fifth, Ozem the sixth, David the seventh.
As to some of the symbolism in the Chronicles geneology, here is Hermeneia's commentary:
Amminadab became the father of Nahshon, the prince of the sons of Judah: As noted under the previous verse, the genealogy from Perez to David has been borrowed from Ruth 4:18–22*.54 In the book of Ruth, Boaz is in the seventh position beginning with Perez, and David is in the tenth position. Both positions often indicate a privileged status within genealogies. Nahshon the son of Amminadab was chosen from the tribe of Judah to assist Moses and Aaron in taking the census of the people in the wilderness period (Num 1:7*; cf. 2:3*; 7:12*, 17*; 10:14*).55 In Num 1:16* he and the other assistants are called leaders or “princes” (נשׂיאי) of their ancestral tribes, which supports the Chronicler’s addition of Nahshon’s title נשׂיא in this verse. Nahshon himself is called the prince of the people of Judah in Num 2:3*.57 The symbolic features of this genealogy (seventh and tenth position) seem to be the guiding principles since clearly there are more than eleven generations in the purported eight hundred year plus years between Judah and David, and more than five generations in the three hundred plus years between Nahshon and David. Hence there has been considerable telescoping in this genealogy.
Klein, R. W. (2006). 1 Chronicles: a commentary. (T. Krüger, Ed.) (p. 95). Minneapolis, MN: Fortress Press.
Here is the JPS commentary, echoing many of the same ideas:
The genealogy spans ten generations. In the Bible, ten generations typically demarcate an epoch (e.g., the period from Adam to Noah in Gen. 5:3–32, and from Shem, Noah’s son, to Abraham in Gen. 11:10–26). Such genealogies, like other genealogies in the ancient world, do not necessarily preserve accurate historical records but rather are constructed to express a community’s ideology about its identity, or to establish the legitimacy of certain structures or persons. In linear genealogies (listing only father and son but not siblings), the names at the beginning and the end mark persons of special prestige or power whose connection with each other needs to be established. The names in between may be obscure, and generations may be telescoped to highlight the important figures. In the case of Ruth 4:18–22, the actual time span stretching between Perez and David would have to be considerably longer than ten generations. An accurate or complete genealogy would thus be expected to include additional names.
Eskenazi, T. C., & Frymer-Kensky, T. (2011). The JPS Bible Commentary: Ruth (First edition, p. 93). Philadelphia, PA: Jewish Publication Society.
So in the process of including Ruth's genealogy of David, Matthew is making the following claims:
(Claim) He is the traditional son of David as per the official (kingly) geneology
(Claim) Christ is the descendent of the founder of Bethlehem (Salma)
Later on, Matthew makes other claims:
Christ is descendent from all of the four redeemed women in the old testament (Ruth, Bathsheeba, Rahab, Tamar) -- which is a fascinating claim and worthy of deep study.
Christ was a member of the group deported.
rant: If I could get anyone to change just one thing in their exegesis, it would be to stop assuming that the Bible is like the President's minutes, where every trip to the bathroom, every meal, etc, is recorded. No, because the Bible says A had sons B and C, it does not mean that there were only 2 sons, or that he had no daughters. Because it says that A ate a meal on Monday and another meal a year later, it does not mean that A only ate twice in one year. I don't know where people are getting this stuff. Take what is written and interpret it as happening, don't assume that something not included didn't happen.
It is a bit of a stretch but it is possible. Jesse lived a long life.
1 Samuel 17:12 Now David was the son of an Ephrathite named Jesse, who was from Bethlehem in Judah. Jesse had eight sons, and in Saul's time he was very old. 13Jesse’s three oldest sons had followed Saul to the war: The firstborn was Eliab; the second, Abinadab; and the third, Shammah. 14 David was the youngest.
On the other hand, John Gill mentions that there could be missing generations.
And Obed begat Jesse. Jesse is thought to be, not the immediate son of Obed, but to be of the fourth generation from him;