9 then his brother's wife shall come to him in the presence of the elders, remove his sandal from his foot, spit in his face, and answer and say, 'So shall it be done to the man who will not build up his brother's house.'

Matthew Henry's Commentary on Deuteronomy 25:9

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.