‘And Judah begat Perez and Zerah of Tamar; and Perez begat Hezron; and Hezron begat Ram; and Ram begat Amminadab; and Amminadab begat Nahshon; and Nahshon begat Salmon; and Salmon begat Boaz of Rahab; and Boaz begat Obed of Ruth; and Obed begat Jesse; and Jesse begat David the king.
This next group leads down from Judah to ‘David the King'. As the ones who follow David are also kings, this specific designation of David as ‘the king' is clearly intended to highlight David and to reveal him as the fountainhead of kingship. It is also to bring out the contrast of ‘David the King' with ‘Jesus the Messiah' (Matthew 1:16, compare Matthew 22:42-45). A greater than David was to be seen as then having come, finally arising in the name of David's house. Furthermore ‘David the King' is in great contrast to ‘Jehoiachin' who heads up in the next section, but is given no title. He had lost his kingship. This was only to be restored at the coming of Jesus the Messiah.
Note the mention of Tamar (Genesis 38:1-30), Rahab (Joshua 2:1 ff) and Ruth. This is unusual because women's names do not usually appear in a genealogy. It is possibly significant that Rahab and Ruth were both Gentiles (and even more significantly a Canaanite and a Moabite, both ‘rejected' races), and Tamar might well also have been, while Rahab and Tamar were also both connected with doubtful sexual behaviour. But each of them, who were not so originally, did became true Israelites by adoption, and all of them revealed their fierce loyalty to God's people. Thus it may be intended that David be seen as having come of combined Israelite/Gentile blood (but truly converted blood), and as having a ‘tainted' ancestry, illustrating the fact that Jesus had come to save His people from their sins (Matthew 1:21; Matthew 1:24), and that that included David. David was not the perfect man that Jesus was. Yet David could be declared to be a man whose heart was acceptable to God (1 Samuel 16:7), demonstrating by this a welcome within the purposes of a merciful God of both Jews and Gentiles, and of the tainted and forgiven, once their hearts are right before Him, for they too were summed up in David.
However the significance of these names must surely also be seen as including the fact that they expressed the faithfulness of their bearers. Tamar went to extreme lengths in order to produce an heir for her dead husband, which was her right and her duty (Judah admits that his was the greater sin). Rahab sacrificed everything in order to help Israel in their battle against Jericho, establishing her life among them (Joshua 6:25). Ruth's faithfulness to Naomi was proverbial so as to produce seed to her deceased husband. Each was concerned with the preservation of Israel. Thus the mention of them together in the first section (the threefoldness indicating completeness) may very much have had this faithfulness to God's purposes in mind, and there can be no doubt that most Jews would have honoured these names. They would have seen them as only adding distinction to the list. A further distinction is that they reveal the particular and unique activity of God at work in producing David the King.
The ‘wife of Uriah' stands alone and unnamed in the second section. Her mention is not seen as adding distinction to the list. Her unfaithfulness resulted in the murder of her husband, and because of her sin her name is seen as ‘cut off'. Her presence in the genealogy helps to explain why the Exile finally followed. It was in fact her son who began the deterioration which resulted in the final collapse of the monarchy. Those in this second section are not noted for their faithfulness to God. Some stood out but even the best failed in the end.
But womanhood is restored in the third section in the mention of Mary of whom was born Jesus. Here pure womanhood is central in the production of the Messiah.
So the idea in the end is that God can take all kinds of materials in the bringing about of His purposes, and can in the process bring about His will. After all, apart from Jesus, every person in the list was a sinner, but it reveals that a gracious God can bring about His purposes through sinners, especially forgiven sinners.
However, probably the main purpose of the inclusion of the women is to remind us that God brings about His purposes in unusual ways. It indicates that we need not therefore be surprised when the Messiah Himself is born in an unusual way. Matthew may have been intending to counter the suggestion that Jesus' inheritance from Joseph was irregular in view of the unusual birth, by indicating that it would not be the only irregularity in the lineage of David, which abounded in such irregularities, including the presence of Canaanites, and a Moabitess (see Deuteronomy 23:3). It is stressing that in spiritual matters nothing is straightforward.
For details of the genealogy as a whole see Ruth 4:18-22; 1 Chronicles 2:3-15. We have shown the names here as ‘modernised', not as shown in the Greek text where they are ‘Hellenised', but thereby less discernible to us. Greek transliterations were in fact varied (as often were Hebrew originals. Names were flexible and altered freely in order to convey ideas). Nahshon is described as ‘a prince of the sons of Judah' in 1 Chronicles 2:10, suggesting his outstanding prominence and importance, and was the prince who led forward the tribe of Judah at the Exodus (Numbers 1:7). Salmon married Rahab, while Boaz, who is mentioned in Ruth 2:1 as a ‘prominent' man, later married Ruth. Unimportant names have been omitted as is common in genealogies.