Sforno on Deuteronomy 16:4/ספורנו על דברים ט״ז:ד׳

1ולא יראה לך שאור בכל גבולך שבעת ימים, even though this was not a requirement on the original Passover in Egypt.

2ולא ילין מן הבשר, so that you should not think that leftovers of the Passover sacrifice were forbidden only on the original occasion, seeing that on that occasion the people were in such a state of haste, that the Torah did not want leftover sacred meat to be at the disposal of the Egyptians.