Yevamot 105 - Rabbinical test
In order to cut the connection between herself and the brothers of her late husband, the widow performs chalitzah: she read verses from the Torah which explain what she is doing, she unties and removes his shoe, and she spits in his direction. Of these actions, only the removal of the shoe is absolutely essential; the other two, while important, will not invalidate the chalitzah if they were not done.
Levi was recommended for a Rabbinical post in a certain village by Rabbi Yehudah the Prince. When Levy arrived, they put him on a platform and asked his the following questions. Can a woman with amputated hands to chalitzah? If she spits blood instead of saliva, what is the law? Levy did not know. They asked him a non-legal question: when an angel tells Daniel " I will tell you what is inscribed in truthful wording ," can there be untruthful wording in Heaven?
Levy went to ask in the Academy. They told him, "Does it say that she shall remove the shoe with her hand? - No! So she can do it with her teeth. Furthermore, does it say that she spits with a spit? - No, it just says that she spits, in any manner." Regarding the last question, the wording is given the appellation of "truthful" when it was accompanies with an oath and cannot be changed. The Talmud then discusses when a Heavenly decree cannot be changed and when it can.
Art: Shoes For Sale by Eugène-Alexis Girardet