Albert Barnes Commentary Ruth 4:21

"and Salmon begat Boaz, and Boaz begat Obed," — Ruth 4:21 (ASV)

Salmon was the father of Boaz - Matthew has preserved the additional interesting information that the mother of Boaz was Rahab (Joshua 2; Joshua 6). It is possible that the circumstance that the mother of Boaz was a Canaanite may have made him less indisposed to marry Ruth the Moabitess.

As regards the whole genealogy in Ruth 4:18-22, it should be remarked that it occurs four times in Scripture, namely, here, (1 Chronicles 2:10–12); (Matthew 1:3–6); and (Luke 3:32–33), and is, of course, of singular importance as being the genealogy of our Lord. One or two difficulties in it still remain unsolved.