From the LCMS website:

Ruth of Moab, the subject of the biblical book that bears her name, is an inspiring example of God’s grace. Although she was a Gentile, God made her the great grandmother of King David (Ruth 4:17), and an ancestress of Jesus himself (Mt 1:5). A famine in Israel led Elimelech and Naomi of Bethlehem to emigrate to the neighboring nation of Moab with their two sons. The sons marriend Moabite women, Orpah and Ruth, but after about ten years, Elimelech and his sons died (Ruth 1:1–5). Naomi then decided to return to Bethlehem and urged her daughters-in-law to return to their families. Orpah listened to Naomi’s but Ruth refused, replying with the stirring words: “Where you go I will go, and where you lodge I will lodge. Your people shall be my people, and your God my God” (Ruth 1:16). After Ruth arrived in Bethlehem, Boaz, a close relative of Elimelech, agreed to be Ruth’s “redeemer” (Ruth 3:7–13; 4:9–12). He took her as his wife, and Ruth gave birth to Obed, the grandfather of David (Ruth 4:13–17), thus preserving the Messianic seed. Ruth’s kindness and selfless loyalty toward Naomi, and her faith in Naomi’s God, have long endeared her to the faithful and redounded to God’s praise for his merciful choice of one so unexpected.