6 Then the first male child she has will take the rights of the brother who is dead, so that his name may not come to an end 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.