Mark 12:19
Teacher, they said, Moses wrote for us that if a man's brother dies and leaves a wife but no children, the man must marry the widow and raise up offspring for his brother — the Sadducees begin with the levirate marriage law of Deuteronomy 25:5–10 — the law designed to preserve a dead man's lineage by having his brother marry his widow. The law is real and the obligation was taken seriously in ancient Israel.