דברים טז:ג פירוש: רש״י, ספורנו, רבנו בחיי וSiftei Chakhamim

לחם עני THE BREAD OF AFFLICTION — i.e. bread that calls to mind the affliction to which they were subjected in Egypt (Sifrei Devarim 130:5).

לא תאכל עליו חמץ שבעת ימים, even though in Egypt the prohibition of eating chametz was in effect for only one day, as our sages pointed out in Pessachim 96.

לא תאכל עליו חמץ, “Do not eat any leavened matter with it.” This refers already to the time when the Passover sacrifice may be slaughtered, i.e. about midday. At that time one must no longer own anything leavened (Ibn Ezra).