Genesis 38:8

38:8 Then Judah said to Onan, “Have sexual relations with your brother’s wife and fulfill the duty of a brother-in-law to her so that you may raise up a descendant for your brother.”

Deuteronomy 25:5-10

Respect for the Sanctity of Others

25:5 If brothers live together and one of them dies without having a son, the dead man’s wife must not remarry someone outside the family. Instead, her late husband’s brother must go to her, marry her, and perform the duty of a brother-in-law. 25:6 Then the first son she bears will continue the name of the dead brother, thus preventing his name from being blotted out of Israel. 25:7 But if the man does not want to marry his brother’s widow, then she must go to the elders at the town gate and say, “My husband’s brother refuses to preserve his brother’s name in Israel; he is unwilling to perform the duty of a brother-in-law to me!” 25:8 Then the elders of his city must summon him and speak to him. If he persists, saying, “I don’t want to marry her,” 25:9 then his sister-in-law must approach him in view of the elders, remove his sandal from his foot, and spit in his face. She will then respond, “Thus may it be done to any man who does not maintain his brother’s family line!” 25:10 His family name will be referred to in Israel as “the family of the one whose sandal was removed.”

Ruth 4:5

4:5 Then Boaz said, “When you acquire the field from Naomi, you must also acquire Ruth the Moabite, the wife of our deceased relative, in order to preserve his family name by raising up a descendant who will inherit his property.”