Deuteronomy 25:5-6
5 When brothers are living together and one of them dies without having had a son, the widow of the dead brother shall not marry a stranger from outside the family; her husband's brother is to come to her and marry her and do the brother-in-law's duty by her. 6 The first son that she bears shall be named after her dead husband so his name won't die out in Israel.
Published by permission. Originally published by NavPress in English as THE MESSAGE: The Bible in Contemporary Language copyright 2002 by Eugene Peterson. All rights reserved.
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.