Tosefta for Exodus 12:19

A woman who collects water that was used by a baker in order to knead [dough] with it for [use] after the Festival, behold, these (i.e., the goods for which she used the dough) are forbidden. Furthermore, women are accustomed to not kneading [dough] after a Festival with water that was heated during the Festival. § [Regarding the question of whether challah (i.e., dough separated for the Kohanim) may be separated during Passover from dough that became impure, and set aside until after Passover, even though it may ferment during Passover, see Pes. 3:3,] Rabbi Eliezer said to Rabbi Yehoshua, how can you possibly say that challah may be separated in a state of impurity during the Festival [and left to ferment], when it is written saying (Ex. 12:19), "leaven may not be found in your houses." Rabbi Yehoshua said to him, behold, [on the seventh day of Passover,] "only that which which may be eaten by every person [may be made by you]" (Ex. 12:16). Rabbi Eliezer said to him, still, the matter hangs in the balance -- who can overbalance it (i.e., what proof can either side bring to prevail in the dispute)? Rabbi Yehoshua said, I will overbalance it, for since what I perform through my own actions (lit., "with my hands") can cause me to violate a negative prohibition, thus [with respect to] that which I leave alone in the state that I found it [without interfering], how can I violate a negative commandment if it was not through my actions?