41 Boaz was sitting at the city gate when the other close relative of Naomi's dead husband came by. 3 Boaz said to him,
Naomi has returned from Moab, and she's selling some land that was owned by her husband Elimelech. Since you are his closest relative, you have the right to buy it. Do you want to?
But if you buy the land from Naomi, you must also marry Naomi's daughter-in-law, Ruth, and have a son with her to carry on Elimelech's name and inheritance.
17 The neighborhood women named him Obed, and said, "A son is born to Naomi. "
Obed was the father of Jesse and grandfather of David.
A few more words about this episode
Naomi's sons married two local Moab women, Orpah and Ruth. (1:4)
David was the great-grandson of Ruth, a Moabite woman. Yet he was the king of Israel, the highest ranking member of "the congregation of the Lord."
An Ammonite or Moabite shall not enter into the congregation of the LORD; even to their tenth generation shall they not enter into the congregation of the LORD for ever. Deuteronomy 23:3
The Ammonite and the Moabite should not come into the congregation of God for ever. Nehemiah 13:1
Ophrah Winfrey said "my name had been chosen from the Bible. My Aunt Ida had chosen the name, but nobody really knew how to spell it, so it went down as 'Orpah' on my birth certificate, but people didn't know how to pronounce it, so they put the "P" before the "R" in every place else other than the birth certificate. On the birth certificate it is Orpah, but then it got translated to Oprah, so here we are." (Academy of Achievement Interview)
I'm too old to get married and make more husbands for you. (1:11)
Deuteronomy 25:5-10 says that if a man dies before having a child, the his wife must have sex with his brother. So Naomi was asking her daughter-in-laws if they should wait until she has a couple more sons to fulfill the command in Deuteronomy.
The King James Version says his "heart was merry," which the Bible's way of saying he was a bit drunk.
He said to her, "Who are you?" (3:9)
Apparently Boaz was so drunk he couldn't recognize Ruth, who he had just met and eaten dinner with earlier that day.
Spread your skirt over me. (3:9)
"Spreading one's skirt" is a biblical euphemism for sexual intercourse." -- Jonathan Kirsch, The Harlot by the Side of the Road: Forbidden Tales of the Bible.
Perform the part of a kinsman. (3:10)
"Performing the part of a kinsman" would be to impregnate and marry her. (See Deuteronomy 25:5-10)
Obed was the father of Jesse and grandfather of David. (4:17)