This Halacha is an excerpt from our Sefer
Buy me here or on Amazon.com
Bedikas Chametz and Bittul Chametz- Understanding the obligation to clean one’s house from Chametz and the effect of Bittul/disownment:
The Biblical obligation: Biblically, if one nullifies his Chametz, and disowns it prior to the 6th hour on Erev Pesach [i.e. Bittul], he is not required to clean his house from Chametz, and the Chametz may remain in his home throughout the entire Pesach. If, however, one does not want to nullify his Chametz and disown it [or did not do so for whatever reason, and the 6th hour has already arrived], then when the time of the owning Chametz prohibition arrives [i.e. the beginning of the 7th hour], he is Biblically obligated to check and search all his possessions for Chametz and completely destroy it from the world.
The Rabbinical obligation: The Sages decreed that nullifying and disowning one’s Chametz before Pesach [i.e. Bittul] is ineffective if it will remain in one’s home, and the Chametz hence remains within one’s ownership, Rabbinically, even if one disowns it. Thus, before Pesach, one must clean all of his possessions from Chametz, just like he would Biblically be required to perform if he did not disown it. One who disowns his Chametz, but does not remove it from his property, transgresses the Rabbinical prohibition of Baal Yiraeh and Baal Yimatzeh. [See the next Halacha for the details of removing the Chametz from one’s property. See Halacha 5E and Chapter 3 Halacha 2 regarding the Rabbinical obligation to destroy less than a Kezayis of Chametz, even if nullified.]
If one searched and then found Chametz on Pesach does he transgress? If one performed the search as required, then even if on Pesach he finds a Kezayis of Chametz which he did not find during his search, he does not retroactively transgress Baal Yiraeh and Baal Yimatzeh over the fact it was unknowingly owned.
The above is a general scope of the obligation of Bedikas Chametz. For the detailed laws of cleaning one’s house for Chametz-See chapter 3. For the detailed laws of Bedikas Chametz and Bittul-See chapter 4.
 Admur 431:2 “If rather than destroying the Chametz one wants to just nullify it and disown it, its meaningless [regarding fulfilling the Torah command] once the Biblical time of the eating and benefit prohibition of Chametz has arrived, which is from midday of the 14th and onwards, as since one is prohibited from benefiting from it, he no longer retains any rights to the Chametz, and [is thus] not his at all [anymore], therefore he can no longer nullify and disown it, [as it is no longer legally owned by him.] However, before the time of the benefit prohibition [arriving], one may nullify and disown the Chametz, and may [after doing so] Biblically leave the Chametz with him in his house throughout all the days of Pesach, as one only Biblically transgresses Baal Yiraeh and Baal Yimatzeh on Chametz that he owns which he has not disowned, as the verse states “You shall not see to you”, that your own Chametz you may not see, however you may see the Chametz of others and that is disowned.”
Other opinions: Some Poskim rule that that even if one did not check his house, and did not nullify his Chametz, he does not retroactively transgress Baal Yiraeh when he finds Chametz on Pesach, and any Chametz which he did not find on Pesach he does not transgress at all, as the Torah only prohibits one from owning known Chametz. [Magen Avraham in his understanding of Rambam and Rosh, brought in Kuntrus Achron 433:3] We do not rule like this opinion [Kuntrus Achron 433:3]
 Biblically, one is able to disown the Chametz until midday, which is the end of the 6th hour of the day and start of the 7th hour. However, Rabbinically, one may only nullify until the start of the 6th hour of day, as states Admur 433:30 “[The ability, to disown the Chametz until midday, is only from a Biblical perspective, however Rabbinically] once the beginning of the 6th hour of the day has arrived, one is no longer able to nullify the Chametz being that the sages decreed that from the [beginning of the] 6th hour and onwards one cannot get any benefit from the Chametz. Thus, starting from the [beginning] of the 6th hour one no longer has any portion or rights to the Chametz, and it is thus not considered his for him to be able to nullify it and disown it.”]
 The reason: As one only Biblically transgresses Baal Yiraeh and Baal Yimatzeh on Chametz that he owns, which he has not disowned, as the verse states “You shall not see to you”, that your own Chametz you may not see, however you may see the Chametz of others and that which is disowned. [ibid]
 Admur 431:3 “[The above ability to do bittul and disown the Chametz before the 6th hour, and then be able to leave the Chametz in his home, is only from a Biblical perspective, however] the sages decreed that doing bittul and disowning the Chametz is meaningless to [avoiding the prohibition of owning] the Chametz even when done before the time of the benefit prohibition arrives [i.e. the 6th hour]. Rather, they decreed that one must search after the Chametz in the holes and hidden areas, if it is common to use these areas throughout the year, and to check and remove any Chametz found within his entire property, and [destroy it or places it in a public area, as will be explained.]”
 The reason for this decree: Admur 431:4: There are two reasons why the sages made the above decree [that the Chametz may not remain in one’s home even if nullified and disowned]:
- First Reason [Rashi]: The reason why the Sages made the nullification ineffective is because nullifying and disowning the Chametz is dependent on ones thought, [meaning] that he disowns the Chametz with a full heart and remove it completely from his heart. Now, since not all people’s thoughts: Daas are alike, and it is [thus] possible that one may be lenient in this and will not disown it with a full heart, and will not remove it from his heart completely, therefore, the sages decreed that nullification and disowning is meaningless unless one actually removes all his Chametz from his property. [1st reason in Admur 431:4]
- Second Reason [Tosafos]: [The reason why they decreed that the Chametz be removed from ones property] is because people are accustomed throughout the year to eat Chametz, and due to this habit it is very possible for him to come to forget about the prohibition of eating Chametz, and he will thus come to eat Chametz if it is lying in his property on Pesach. Therefore, the sages required that one search and check for Chametz and remove it. [2nd reason in Admur 431:4]
The main reason: [Although these two reasons are mentioned] the main reason of the sages for one to search for Chametz, despite having nullified it, is because of a decree that perhaps one will come to eat it on Pesach. [Admur 433:19]
The reason it does not help to place the Chametz behind a Mechitza: The reason the Sages allowed one to place the Chametz of a gentile behind a Mechitza, even though one who disowns Chametz must destroy it completely from the home, is because by a gentile’s Chametz, one is more hesitant to eat from it, and thus placing it behind a Mechitza suffices. However, by Chametz of Hefker, that was disowned, one is not hesitant to eat from it even if a Mechitza is placed. [Admur in gloss on Kuntrus Achron 440:11]
 See Admur 433:34; 434:6; 435:4
The concept of Baal Yiraeh Ubal Yimatzeh Midivreiy Sofrim: An innovative idea brought in the Shulchan Aruch of Admur is the concept of a Rabbinical transgression of Baal Yiraeh and Baal Yimatzeh. Meaning, that if one does not check and remove the Chametz from his home he is not transgressing a plain Rabbinical decree which obligates one to do so, but rather he actually transgresses the Biblical concept of Baal Yiraeh and Baal Yimatzeh from a Rabbinical standpoint. The practical ramification between whether one learns the decree is to destroy the Chametz or learns that it is a Rabbinical Baal Yiraeh prohibition, is regarding a case that one who nullified his Chametz before Pesach and then found Chametz on Pesach. Does one say a blessing when destroying this Chametz? If one learns like the former approach, then a blessing is not recited, as we never recite a blessing prior to destroying a non-Kosher item simply to avoid coming to eat it. If, however, one learns like the latter approach, then a blessing is required, just as a blessing is recited prior to performing all Rabbinical commands. [Admur 435:4; 446:2; Kuntrus Achron 1] Practically, Admur learns like this second approach. However, today that we in any event sell our Chametz, when Chametz is found during Pesach no blessing is said upon destroying it, as will be explained in its relevant section.
A deeper understanding: The decree of the sages that one must remove Chametz from his property was not worded as “that one must remove the Chametz from his home”. Rather it was worded that “Nullification does not help”, and then consequently one must remove the Chametz from his home, as Biblically one must remove Chametz from his home if he owns it. Thus, in a case that one has disowned and removed his Chametz into a public area before the 6th hour, then he does not need to destroy it, as even when we disqualify this nullification, one still does not need to Biblically destroy the Chametz, being that it is not in his property at all, and therefore there is no obligation to destroy it. Accordingly, it is greater understood why Admur holds of the concept of Baal Yiraeh and Baal Yimatzeh Midivreiy Sofrim, as since the sages disqualified the nullification, there remains a Biblical prohibition of Baal Yiraeh. [See Admur 445:1-2]
 Admur 433:12; Rashi; Ran; Pri Chadash
Other opinions: Some Poskim rule that even after one has done Bedikah, he must Biblically nullify the Chametz, and if he does not do so, then if he finds a Kezayis of Chametz on Pesach, he has retroactively transgressed the prohibition of Baal Yiraeh and Baal Yimatzeh. [Rambam 3:4; Rosh, as learns Pri Chadash, however, according to the Magen Avraham 433, the Rosh holds like Rashi and Ran; Tur 433, as learns Peri Chadash, however, the Taz learns that even according to the Tur one does not transgress retroactively.] According to this opinion, the Bedikah does not help at all Biblically for unknown Chametz unless one also did Bitul. [Kuntrus Achron 3] Other Poskim rule that that even if one did not check his house, and did not nullify his Chametz, he does not retroactively transgress Baal Yiraeh when he finds Chametz on Pesach, and any Chametz which he did not find on Pesach he does not transgress at all, as the Torah only prohibits one from owning known Chametz. [Magen Avraham in his understanding of Rambam and Rosh, brought in Kuntrus Achron 433:3]
 The reason: Being that it was not at all his fault [Lit. Anus Hu], as he checked for Chametz as was Halachically required. [Admur ibid] However, if one did not check for Chametz and did not nullify it, he does transgress Baal Yiraeh on all the unknown Chametz which he owns in the house. [Admur ibid] However, the Magen Avraham learns in the Rambam and Rosh that even if one did not check his house, and did not nullify his Chametz, he does not retroactively transgress Baal Yiraeh when he finds Chametz on Pesach, and any Chametz which he did not find on Pesach he does not transgress at all, as the Torah only prohibits one from owning known Chametz. We do not rule like this opinion [Kuntrus Achron 433:3]