The Gospel of Matthew leads us to three points in the genealogy of Jesus when it brings into view the names of three women who have caused tiredness and shame to the commentators of the Old Testament. We, on our part, condemn nobody, but we observe man's wicked trends and continue in repentance of our own sins.
Matthew did not mention the names of Sarah nor of other famous women whom all the Jews are proud of, but he mentions the names of the women whom the Jews were unable to be proud of: "Tamar" was mentioned to indicate that the salvation of God is planned for sinners (Genesis 38:11-14); "Rahab" was mentioned to indicate that the salvation for sinners is by faith (Joshua 2; Hebrews 11:31); "Ruth" was mentioned to indicate that this salvation is by grace without the law (Deuteronomy 23:3; Romans 3:21-30); and "Bath-Sheba" was mentioned to indicate that the salvation of God to believers is by grace and that such salvation is everlasting (2 Samuel 11 + 12; Psalm 23:3; Hebrews 10:38-39).
We do not precisely know some of the names mentioned in the genealogy of Jesus today. However we know that Rahab, the heathen prostitute received the spies and protected them because God showed her that he surrendered her city Jericho to the hands of the oncoming people. After the city was conquered, one of those spies married her and she became a grandmother of Christ. Tamar brought non-Jewish blood into King David and Jesus. Rahab did the same, and such did Ruth, because the Spirit of God wished to prove that he was not keeping to a racial thinking, but also desires to save Gentile sinners (Joshua 2:1-21; Hebrews 11:31).
Boaz was a straight man. He did not take advantage of the distress of Ruth, the widow, but ordered his servants to leave the grain of the harvest for her to gather and eat because he knew what a faithful friend she was to her mother-in-law (the mother of her late husband). After that, he married her though she was a foreign woman and she became the mother of David’s grandfather. She was considered unclean according to Jewish law but all men are equal to God (Ruth 2:4).
The most horrible sin in the history of the ancestors of Jesus was one committed by David, the prophet. He desired the wife of Uriah, one of his soldiers, as she was taking a bath on the roof of her house. He sent messengers and brought her to his palace, and asked the commander of his army to find a plan to let Uriah, her husband, be killed in an ambush of the enemy in order to cover the shame of the king. But God uncovered the adultery and the murder in his servant and threatened to kill him. Nothing could save him but the sincere and immediate repentance and the belief in God’s grace for the humble and repentant (Psalm 51). The mercy did not leave him. He married her legitimately, and God gave them a son, wise Solomon, inasmuch as the marriage was purified through sincere repentance.