Charles Ellicott Commentary Matthew 1:5

"and Salmon begat Boaz of Rahab; and Boaz begat Obed of Ruth; and Obed begat Jesse;" — Matthew 1:5 (ASV)

Rahab — The Old Testament records are silent regarding the marriage of Salmon with the harlot of Jericho. When those records were compiled, it was probably considered a stain rather than an honor, but the fact may have been preserved in the traditions of the house of David. It has been conjectured that Salmon may have been one of the two unnamed spies whose lives Rahab saved when he was doing the work that Caleb had done before him. The mention of Rahab in James 2:25 and Hebrews 11:31 shows that her fame had grown by the time St. Matthew wrote. The Talmudic legends, curiously enough, count eight prophets among her descendants—including Jeremiah and Baruch—but not anyone from the line of David. Assuming the probable connection between St. Matthew and St. James (as shown in the Introduction to this Gospel), the mention of Rahab by both is an interesting coincidence.

Booz — The succession is the same as in Ruth 4:21. The new fact of Salmon’s marriage explains several features of that history: the readiness with which Naomi's sons married two Moabite women, the absence of any repugnance to such a union on the part of Boaz, and perhaps the reference to Tamar in the blessing of Ruth 4:12. Salmon seems to have been the first of his house to own land at Bethlehem (1 Chronicles 2:54), gaining it partly through his adoption into the family of Caleb.