My Old Testament professor would say that if you don’t find curious things in the Bible, it means you aren’t paying attention. So, it is in Matthew’s genealogy that I ran across this, while reading Joshua (I originally was preparing for my Sunday School lesson). This was all triggered because of the song Matthew’s Begats by Andrew Peterson.
In Matt.1:5 we read that Salmon begot Boaz by Rahab. This Rahab is presumably the Rahab of Joshua, the prostitute who harbors the spies and is spared when Jericho falls. Otherwise, if it’s some unknown Rabah – why mention her? That seems plausible… right?
Problem 1. Neither the Old Testament or the Pseudepigrapha (to my reading) metions it (see the genealogies at Ruth 4:20-21; 1 Chr. 2:1-11) . So where did it come from? How did Matthew know about it?
Problem 2. The other times Rahab is mentioned in the New Testament (Heb. 11:13 and James 2:25) it’s actually spelled differently in Greek (and still no mention of her being in the genelogy of David and thus Christ). In Heb. 11:13 and James 2:25 it’s spelled Ra’ab, which is what the Greek OT (LXX) does when it translates Rahab. In Matthew it’s spelled Rachab (with a Scottish “ch” there) which is actually how the Hebrew is spelt.
There is apparently some extra-biblical tradition that I haven’t been able to investigate in Talmudic Judaism about Rahab’s decendents. If I can ever get a hold of a book, I’ll let you know what I find.
What does everyone think about this? Strange? No? No concern?
 See The Gospel According to Matthew in the Pillar New Testament Commentary series page 24. He notes the same strange absence of this tradition in Judaism.
 The book is Marshall Johnson’s The Purpose of the Biblical Genealogies (see pp. 162-65), if you’d like to ship me the copy – let me know!