Deuteronomy 25:5-6

Lexham English Bible

⁵ “When brothers dwell together and one of them dies and has no son, the wife of the deceased shall not become the wife of a man of another family;^[a] her brother-in-law shall have sex with her,^[b] and he shall take her to himself^[c] as a wife, and he shall perform his duty as a brother-in-law with respect to her. ⁶ And then the firstborn that she bears shall represent his dead brother,^[d] so that his name is not blotted out from Israel.