No leaven shall be seen with you: this simply means that all leaven (or yeast) was to be removed from every household. Leaven was seen as an impure substance, and the word was sometimes used as a figure of evil.

The second part of the verse requires that the whole animal offered in sacrifice be eaten the first night, which seems to conflict with the instructions in verse 3. It may be, however, that we are to understand that a fresh animal was slaughtered each night of the seven-day festival.

The flesh which you sacrifice: more naturally, “the meat of the animal that you offered in sacrifice.” The meaning of nor shall any of the flesh … remain is that the whole animal had to be eaten that very same evening.

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on Deuteronomy. (UBS Helps for Translators). New York: UBS, 2000. For this and other handbooks for translators see here .