שמות יג ,יד: מַה־זֹאת
The Sforno departs from the usual interpretation that this question to the simple son, and explains that this is a legitimate, even learned, question. The question is what is the reason (of the previous verse) that the redemption of the firstborn donkey considering that it is an unclean animal and has no sanctity of the body that can devolve on it? Why break its neck if it is not redeemed?
The answer given by the Torah בחוזק יד (by a strong hand) would be interpreted as referring to the firm, insistent pressure of the Egyptians to leave quickly. The Jews could not carry all the possessions and gifts on their own back and normally even the donkeys would have been unable to carry so much. Since miraculously the donkeys accomplished this feat, their species took on a degree of sanctity; hence the requirement to redeem or dispose of the firstborn of the donkey.
