The NIV Cultural Backgrounds Study Bible suggests that the common thread between all of these women is that they have associations with Gentiles. Rahab was a prostitute in Canaan, Bathsheba was married to a Hittite, Ruth resided in Moab, and Tamar had a name of Hebrew origin. The women's nationalities are not necessarily mentioned. The suggestion is that Matthew may be preparing the reader for the inclusion of the Gentiles in Christ's mission. Others point out an apparent element of sinfulness: Rahab was a prostitute, Tamar posed as a prostitute to seduce Judah, Bathsheba was an adulteress, and Ruth is sometimes seen as seducing Boaz—thus Matthew emphasizes God's grace in response to sin. Still others point out their unusual, even scandalous, unions—preparing the reader for what will be said about Mary. None of these explanations, however, adequately befits all four women.