Deuteronomy 25:9

Loose his shoe; partly as a sign of his resignation of all his right to the woman, and to her husband's inheritance; for as the shoe was a sign of one's power and right, Psalms 60:8, Psalms 108:9; so the parting with the shoe was a token of the alienation of such right, and that he would not, and henceforth might not, enter upon his brother's land; and partly as a note of infamy, to signify that by this unnatural and disingenuous action he was unworthy to be amongst free-men, and fit to be reduced to the condition of the meanest servants or captives, who used to go barefoot, Isaiah 20:2,4. Spit in his face, as a return of his contempt upon himself. See Numbers 12:14 Isaiah 1:6 Isaiah 26:67; Isaiah 27:30. This was not done, Rth 4, either because he was not a brother, but a remoter kinsman, and so deserved less shame; or because Ruth did not prosecute him to the utmost, but freely consented to this exchange. Build up; a phrase oft used for the procreation of children, and the increase of a family. See Genesis 16:2 Exodus 1:21 1 Kings 11:38 1 Chronicles 17:25.