Fausset's Bible Dictionary
Salmon. Son (descendant) of Nahshon, prince of Judah, father (forefather) of Boaz (Ruth 4:20-21; 1 Chronicles 2:50-51; 1 Chronicles 2:54-55; Matthew 1:4-5; Luke 3:32). Of the sons of Caleb (i.e., by residence or marriage becoming head of Bethlehem in Caleb's territory, Salma was reckoned of Caleb's family). Father, i.e. founder or headman, of Bethlehem. Salma took Rahab of Jericho to be his wife. The Netophathites also, Joab's house, the Zorites, etc., had Salma as their head. Doubtless one or more links in the genealogy between Nahshon and Salma, and again between Salma and Boaz, have been passed over, possibly one also between Obed and Jesse. The chain from Perez to David consists of ten links, five (from Perez to Nahshon) belonging to the 430 years' sojourn in Egypt, and five (from Salma to David) belonging to the 476 between the Exodus and David's death. This symmetrical division, as well as the limitation of the whole genealogy to ten, is evidently intentional, ten being the number sealing the genealogy as a perfect completed whole.
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Fausset, Andrew R. Entry for 'Salma'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/s/salma.html. 1949.