TT #750 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:09
Then his yevamah shall approach him in the presence of the elders, and draw his shoe off his foot, and spit in his face, and respond and say: “Thus shall be done to the man who will not build up his brother’s house.”
Torah Temimah points to Yevamot / Sifrei.
TT lemma: כָּכָה יֵעָשֶׂה לָאִישׁ.
חָלְצָה וְלֹא רָקְקָה וְלֹא קָרְאָה – חֲלִיצָתָהּ כְּשֵׁרָה, דַּאֲמַר קְרָא כָּכָה יֵעָשֶׂה לָאִישׁ – כָּל דָּבָר שֶׁהוּא מַעֲשֶׂה בָּאִישׁ מְעַכֵּב.
English: If she drew off the shoe but did not spit and did not recite — her chalitzah is valid, for Scripture says “thus shall be done to the man” — whatever is an act performed upon the man is indispensable.
On the daf / in context: Only the act that is done to the man’s body (removing the shoe) is indispensable; spitting and recitation are not absolute requirements for validity after the fact.
Derash identifying the indispensable element of the rite.
The removal of the shoe is the indispensable act; omission of spitting or of the formula does not invalidate the chalitzah after the fact.