כֻּלָּם֙ מְנָ֣אֲפִ֔ים כְּמ֣וֹ תַנּ֔וּר בֹּעֵ֖רָה מֵֽאֹפֶ֑ה יִשְׁבּ֣וֹת מֵעִ֔יר מִלּ֥וּשׁ בָּצֵ֖ק עַד־חֻמְצָתֽוֹ׃
Mereka semua berzina, bagaikan tungku yang dipanaskan oleh tukang roti; ia hanya berhenti mengobarkannya sejak adonan diremas sampai adonan itu beragi.
Sforno
תאכל עליו מצות, seeing it was an offering commemorating the redemption, something that took place in a short moment in time, it is not appropriate to eat chametz, something which by definition requires time in order to become leavened. (compare Hoseah 7,4, “from kneading the dough until it has been baked”).
Rabbeinu Bahya
טרם יחמץ, “before it could become leavened.” Something similar will occur in the future. This is what Hoseah 7,4 meant when he said: “who desists from the kneading of the dough to its leavening.”