5 "When brothers live together and one of them dies and has no son , the wife of the deceased shall not be married outside the family to a strange man . Her husband's brother shall go in to her and take her to himself as wife and perform the duty of a husband's brother to her. 6 "It shall be that the firstborn whom she bears shall assume the name of his dead brother , so that his name will not be blotted out from Israel .
Matthew Henry's Commentary on Deuteronomy 25:5-6
Commentary on Deuteronomy 25:5-12
(Read Deuteronomy 25:5-12)
The custom here regulated seems to have been in the Jewish law in order to keep inheritances distinct; now it is unlawful.