Deuteronomy 25:5
If brethren dwell together, and one of them die, and have no child, the wife of the dead shall not marry without unto a stranger: her husband’s brother shall go in unto her, and take her to him to wife, and perform the duty of an husband’s brother unto her.
Cross-reference
Genesis 38:8 records Judah commanding Onan to perform the levirate duty—the OT precedent for this law.
In Genesis 38:9, Onan's refusal to raise offspring for his brother is the classic violation of the levirate duty, showing why the law was needed.
In Ruth 3:9, Ruth asks Boaz to act as kinsman-redeemer, directly invoking the spirit of the levirate duty to continue the family line.
In Ruth 4:5, Boaz explicitly takes Ruth to 'raise up the name of the dead,' fulfilling the levirate principle from Deuteronomy 25:5.
Matthew 22:24 quotes the levirate law directly, as the Sadducees use it to test Jesus about the resurrection.
Mark 12:19 also cites the levirate law, presented by the Sadducees in their question to Jesus.
Luke 20:28 quotes the same levirate law, used by the Sadducees to challenge Jesus on the resurrection.
In Leviticus 18:16, sex with a brother's wife is forbidden—contrasting with Deuteronomy 25:5, which commands it after the brother's death.
In Ruth 3:13, Boaz offers to fulfill the kinsman-redeemer role, directly applying the levirate marriage law from Deuteronomy 25:5.
Matthew 14:4 condemns Herod's marriage to his brother's living wife, contrasting the levirate law which permits marrying a deceased brother's widow.
In Ruth 1:11, Naomi says she has no more sons to be husbands—highlighting the practical limitation of the levirate law.
In Ruth 2:20, Naomi identifies Boaz as a close relative and redeemer, setting the stage for a levirate-style marriage.