Then Boaz said, "On the day you buy the land from Naomi and also from Ruth the Moabitess, you must also acquire the widow of the deceased in order to raise up the name of the deceased on his inheritance."

Matthew 22:24
"Teacher," they said, "Moses declared that if a man dies without having children, his brother is to marry the widow and raise up offspring for him.

Genesis 38:8
Then Judah said to Onan, "Sleep with your brother's wife. Perform your duty as her brother-in-law and raise up offspring for your brother."

Deuteronomy 25:5
When brothers dwell together and one of them dies without a son, the widow must not marry outside the family. Her husband's brother is to take her as his wife and fulfill the duty of a brother-in-law for her.

Deuteronomy 25:6
The first son she bears will carry on the name of the dead brother, so that his name will not be blotted out from Israel.

Deuteronomy 25:7
But if the man does not want to marry his brother's widow, she is to go to the elders at the city gate and say, "My husband's brother refuses to preserve his brother's name in Israel. He is not willing to perform the duty of a brother-in-law for me."

Then said Boaz, What day you buy the field of the hand of Naomi, you must buy it also of Ruth the Moabitess, the wife of the dead, to raise up the name of the dead on his inheritance.