Bitul Chometz – A Brief History by Rabbi Yair Hoffman

Five Towns Jewish Times  According to Torah law, we can dispose of our Chometz before Pesach either by Biur—destruction or by Bitul—negation. By Rabbinic law, we must do both. We are all familiar with the text, we recite it in the evening after the search for Chometz, and again in the morning while we burn it.

What is perhaps shocking is that no where in the Babylonian Talmud is this formulation found. There is certainly an obligation to annul the Chometz, but it seems from the Gemorah (See Psachim 6b) that this is a thinking process that did not necessarily have to be verbalized. The Ramban actually rules that one does not require a verbal declaration (See Ramban, Psachim 7a, 31b^[1]). The Jerusalem Talmud (Psachim 2:2), however, states just the opposite. There, Rav is quoted as ruling that one must recite the formula “All Chometz that is in my house that I am not aware of shall be annulled.”

The Rosh and the Rif, however, explain our Gemorah as stating that the annulment does require an actual verbal formulation. They differ slightly as to the verbal formula. There are actually four changes: [...]

Another question that exists in regard to the annulment is whether the Bitul can be annulled through a Shliach, through a messenger^[3]. The Baal HaIttur holds that since a messenger is like the person throughout the entire Torah, a messenger can annul the Chometz of someone who sent him. The Rashba, the Ritva and the Nimukei Yoseph disagree and write that the actual owner of the Chometz must be the one who annuls it. The TaZ rules in accordance with the lenient opinion and states that someone who does utlize a messenger to annul, in all probability, has a reason for it. He is concerned that he may become busy or simply forget to annul it. His father-in-law, the Bach, however, was stringent. [...]