And Salmon begat Boaz of Rahab; and Boaz begat Obed of Ruth; and Obed begat Jesse;
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Theophylact of Ochrid
Some believe Rachab to be that Rahab the harlot who received the spies of Jesus son of Nave [i.e. Joshua son of Nun]. She saved them, and was herself saved as well. He mentions her to show that just as she was a harlot, so, too, was the congregation of the nations, for they went whoring in their practices. But all those who accepted the spies of Jesus, that is, the apostles, and were convinced by their words, were saved from among the nations.
Ruth was a foreigner but nevertheless she was married to Boaz (Ruth 4:13-17). So, too, the Church is from among the Gentiles. For like Ruth, these Gentiles had been foreigners and outside the covenants, yet they forsook their people, their idols, and their father, the devil. And as Ruth was wed to Boaz of the seed of Abraham, so too was the Church taken as bride by the Son of God.