To DO THE DUTY OF A BROTHER-IN-LAW — one Hebrew verb, built from yabam, 'a husband's brother.' When a man died childless his brother was to marry the widow, and their first son counted as the dead man's, so his name was not blotted out and the widow was not left destitute (38:8). Genesis shows the custom already operating two centuries before Deuteronomy 25:5-10 writes it into law — including the shaming ceremony for a brother who refuses. Everything in Genesis 38 turns on that refusal: Onan takes the marriage and withholds the duty, and Judah then withholds Shelah. The institution drives the whole book of Ruth, where Boaz performs the nearer kinsman's declined obligation. KJV 'perform the duty of an husband's brother unto her'; NWT 'perform brother-in-law marriage with her.' ⭐ Deuteronomy 25:5–10 is now on these pages. The verb stands in three verses of the Hebrew Bible — Judah's order to Onan, and Deuteronomy 25:5 and 25:7 — and the feminine noun, yevamah, the brother's widow, in Deuteronomy 25:7 and 25:9 and at Ruth 1:15, where Naomi calls Orpah Ruth's sister-in-law with it. ⚠ The Greek says seed where Deuteronomy's Hebrew says son, and the Sadducees of Matthew 22:24 quote the law in Genesis 38:8's words, raise up seed for his brother, not Deuteronomy's raise up a name. → first discussed at Gen 38:8