Ruth's story is told in the Book of Ruth — a Moabite widow who returned with her mother-in-law Naomi to Bethlehem, married Boaz, and became an ancestor of King David.
Key passages:
"And Ruth said, Intreat me not to leave thee, or to return from following after thee: for whither thou goest, I will go; and where thou lodgest, I will lodge: thy people shall be my people, and thy God my God:" — Ruth 1:16
"The LORD recompense thy work, and a full reward be given thee of the LORD God of Israel, under whose wings thou art come to trust." — Ruth 2:12
"So Boaz took Ruth, and she was his wife: and when he went in unto her, the LORD gave her conception, and she bare a son." — Ruth 4:13
"And the women her neighbours gave it a name, saying, There is a son born to Naomi; and they called his name Obed: he is the father of Jesse, the father of David." — Ruth 4:17
Read the full account in Ruth — the book is only four chapters.