Deuteronomy 25:9
9 then shall his brother's wife come unto him in the presence of the elders, and loose his shoe from off his foot, and spit in his face; and she shall answer and say, So shall it be done unto the man that doth not build up his brother's house.
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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.