Pesachim 35B

ומי פירות אין מחמיצין.

and fruit juice does not cause dough to be leavened. Therefore, dough prepared with these liquids is not considered full-fledged leavened bread.

יוצא בדמאי ובמעשר וכו׳. דמאי הא לא חזי ליה! כיון דאי בעי מפקר לנכסיה הוי עני ואוכל דמאי ⁠— השתא נמי חזי ליה.

The Talmud turns to the cases of the Mishnah. The Mishnah taught that one can fulfill his obligation to eat matza with doubtfully tithed produce and with produce of the first tithe, from which teruma has been separated. The Talmud asks: Can one really fulfill his obligation with doubtfully tithed produce? It is not suitable for him to eat. The rabbis prohibited the eating of doubtfully tithed produce that has not been tithed. The Talmud answers: Since, if one so desires he may renounce all his property, thereby becoming a poor person who is permitted to eat doubtfully tithed produce, now too it is suitable for him, even though he did not declare his property ownerless. Consequently, if he used doubtfully tithed produce as matza, he has fulfilled the mitzva after the fact.

דתנן: מאכילין את העניים דמאי, ואת אכסניא דמאי. ואמר רב הונא: תנא בית שמאי אומרים: אין מאכילין את העניים דמאי ואת האכסניא דמאי, ובית הלל אומרים: מאכילין.

As we learned in a Mishnah: One may feed the poor doubtfully tithed produce, and he may also feed Jewish soldiers [akhsanya] who lodge with him doubtfully tithed produce. And Rav Huna said that it was taught that Beit Shammai say: One may neither feed the poor doubtfully tithed produce, nor feed soldiers doubtfully tithed produce. And Beit Hillel say: One may feed these groups doubtfully tithed produce. This Mishnah indicates that doubtfully tithed produce is not prohibited to the same extent as entirely untithed produce, as in certain situations the prohibition pertaining to doubtfully tithed produce does not take effect.