6 The first son she bears to him will be considered the son of the dead brother, so that his name will not be forgotten in Israel.

Matthew Henry's Commentary on Deuteronomy 25:6

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.