||His sister-in-law shall then approach him before the elders, take off his shoe and spit toward his face. She shall then declare, 'This is what shall be done to the man who will not build up a family for his brother.'
Venigshah yevimto elav le'eyney hazekenim vechaltsah na'alo me'al raglo veyarkah befanav ve'anetah ve'amerah kachah ye'aseh la'ish asher lo-yivneh et-beyt achiv.
The right shoe (Yevamoth 104a). There are many laws regarding exactly how the special shoe used in this ceremony must be constructed (See Evven HaEzer 169:14-23).
Some say that the reason that his shoes are removed is so that he shall be like a mourner or one who is excommunicated (Hagahoth Maimonioth, Yibbum 4:8 #9; Beth Sh'muel 169:43). Others say that was done in order to humiliate the man (Moreh Nevukhim 3:49). According to others, it was to release any claim the brother may have had to the dead one's inheritance (Rashbam; Chizzkuni; cf. Ruth 4:7). Still another opinion states that it was to show that the woman was not free to remarry up to this time, and therefore had to perform such services for the man (Chinukh 599). Others say that it is as if she is pleading for the man to marry her (Paaneach Razah).
(Yevamoth 106b; Rashi).