The twentieth commandment in the Torah is the prohibition presented in the Book of Shemot (13:7), “Ve’lo Yera’eh Lecha Hametz Ve’lo Yera’eh Lecha Se’or,” which forbids having in one’s possession during Pesach either Hametz (leavened products) or Se’or (a leavening agent). One who has either of these two products in his possession at any point during Pesach is in violation of this Biblical prohibition. The Sefer Ha’hinuch notes that this prohibition is punishable by Malkut (lashes) if it is violated through an action. There is a famous principle that one who transgresses a Biblical prohibition is liable to Malkut only if he violates the command by performing a concrete action, whereas one who transgresses a “Lav She’en Bo Ma’aseh” – a prohibition which does not involve a concrete action – is not liable to Malkut. Therefore, if a person had Hametz in his possession before Pesach, and he failed to eliminate it before Pesach, thus violating this prohibition through inaction – by neglecting to destroy or remove the Hametz before Pesach – he is not liable to Malkut. However, if somebody went out and acquired Hametz on Pesach, or turned flour into Hametz on Pesach, then since he transgressed this prohibition through a concrete action, he is liable to Malkut. The Kessef Mishneh (commentary to the Rambam’s Mishneh Torah by Maran Rav Yosef Karo, 1488-1575) makes a famous comment (Hilchot Hametz U’masa 1:3) asserting that according to the Rambam, the prohibition of “Lo Yera’eh” is violated only if the Hametz is visible. Since the command “Lo Yera’eh” literally means that Hametz “shall not be seen” in one’s property, the Rambam maintained that if one has Hametz stored in a concealed location, such as if it is buried underground, he does not transgress the prohibition of “Lo Yera’eh.” He has violated the related prohibition of “Lo Yimaseh,” which means that Hametz should not be present in the home, but he has not transgressed the command of “Lo Yera’eh.” Interestingly, the Rosh (Rabbenu Asher Ben Yehiel, Germany-Spain, 1250-1327), in Masechet Pesahim (1:9), disagreed, and maintained that the command “Lo Yera’eh” should not be taken so literally as to be limited to visible Hametz. He explains that any Hametz which is present in one’s possession, and thus could potentially be seen, suffices for one to violate this command. The Minhat Hinuch raises the question of whether the Kessef Mishneh’s theory would apply also to a blind person. Conceivably, if the command of “Lo Yera’eh” is to be taken literally, as forbidding the sight of Hametz, then it would be limited to those capable of seeing it, and a blind person with Hametz in his possession would not be in violation of this command. On the other hand, one might argue that since the Hametz itself is visible, and can be seen by others, the blind person who has it in his possession is in violation of “Lo Yera’eh.” (This assumes, of course, that blind individuals are bound by the Torah’s commands, which is a topic for a separate discussion.) The Minhat Hinuch leaves this question unresolved.