Yevamos, Chapter 12, Mishnah 2. We continue with the mitzvah of chalitzah. This mishnah lists examples of types of shoes and manners of chalitzah that are valid after the fact, but should not be used at the outset.
Forms of chalitzah that are valid after the fact:
"Chalitzah b'sandal she'eino shelo" - a sandal borrowed from someone else.
"O b'sandal shel eitz" - a wooden shoe covered with leather, since in any case it must contain leather.
"O b'shel s'mol b'yamin" - a left shoe placed on the right foot.
In all of these - "chalitzatah kesheirah" - her chalitzah is valid.
The same applies to the size of the shoe:
"B'gadol she'yachol l'haleich bo" - a shoe larger than his foot, provided that he is able to walk in it and it does not slip off as he walks.
"O b'katan she'chofeh es rov raglo" - a shoe somewhat smaller than his foot, but which covers most of the foot.
In these too "chalitzatah kesheirah" - her chalitzah is valid, though this is not the way it should be done at the outset.
"Chalitzah balaylah" - chalitzah at night:
According to the first Tanna, "chalitzatah kesheirah" - her chalitzah is valid, since chalitzah is comparable to the conclusion of a court case - the final stage of a Torah judgment and the resolution of the halachic dispute. We find in Sanhedrin that monetary cases are judged by day but may be concluded at night, provided they began by day. And indeed chalitzah does contain a monetary element, for the yevamah collects her kesubah upon receiving the chalitzah. Therefore chalitzah at night resembles the conclusion of a monetary case, and it is valid.
Rabbi Eliezer disagrees and holds that the entire chalitzah must be performed by day, because it more closely resembles the beginning of a monetary case, which may be judged only by day.
"B'smol" - chalitzah from the left foot:
Earlier the mishnah dealt with a left shoe placed on the right foot; here the discussion is about removing the shoe from the left foot itself, and in that case "chalitzatah pesulah" - her chalitzah is invalid. This is derived from a gezeirah shavah, "raglo" "raglo," from the metzora: in the process of the metzora's purification, the blood of the offering and the oil are placed on the thumb of his right foot, and from here we learn that in chalitzah as well the foot must be the right one.
Rabbi Eliezer validates it: at the outset one should perform chalitzah on the right foot, but if he performed it on the left foot - after the fact the chalitzah is valid.
In summary: in this mishnah we learned which forms of chalitzah are valid after the fact even though they are not the proper way at the outset - a borrowed sandal, a wooden sandal, a left shoe on the right foot, a large shoe that he can walk in, and a small shoe that covers most of the foot; the dispute between the first Tanna and Rabbi Eliezer regarding chalitzah at night, whether its law is like the conclusion of monetary cases or like their beginning; and the law of chalitzah from the left foot, which is invalid based on the gezeirah shavah "raglo" from the metzora, while Rabbi Eliezer validates it after the fact.