Siman 64

We learned in a Mishna (15a): One who reads out of order has not fulfilled his obligation. That is to say: that he read the second verse before the first, as it is written: "And they shall be" — they shall remain in their established state (Megillah 17b). And this applies specifically to the verses, but if he preceded "And it shall come to pass if you surely hearken" to "Shema," or "And the Lord spoke" to "Shema" or to "And it shall come to pass if you surely hearken" — he has fulfilled his obligation, for they are not arranged in the Torah one after the other. Therefore, even though the sages ordained to read "Shema" first, and afterwards "And it shall come to pass if you surely hearken," and afterwards "And the Lord spoke," nevertheless, this is not a requirement post facto.

And there is a question regarding this: Since the reason is because of "and they shall be," as I have written, this is well for "Shema" and "Vehaya Im Shamoa," where "and they shall be" is written. But the parsha of tzitzit, in which "and they shall be" is not written, from where do we know that he has not fulfilled his obligation if read backwards? And should you say that this is indeed so, if so, the poskim should have explained this, and from the fact that they were silent, it implies that it refers to all three parshiot. And one may further ask: For the one who holds that by Torah law one fulfills the obligation of the recitation of Shema with the first verse or the first parsha, what prohibition is there when he reads backwards? And if we say that by rabbinic law he has not fulfilled it, if so, let it also be a requirement in the parshiot? But in truth, from this there is a proof to what we wrote in siman 58, section 16, that all the parshiot are by Torah law, see there. And one should also not ask: Why in the writing of tefillin and mezuzot is it invalid if they are not in order even regarding the parshiot, as I wrote at the beginning of siman 32, and why in their recitation do we not insist on the order of the parshiot? And there is one of the great authorities who raised this difficulty (Pri Megadim). But in truth, it is not comparable, for there they are all one mitzvah, as this without that is nothing. Therefore, we insist on the order written in the Torah, even though they are not adjacent to one another in the Torah. But in their recitation, where each parsha is a matter unto itself—the first for the acceptance of the yoke of the Kingdom of Heaven and the second for the yoke of mitzvot—we are not concerned if he preceded this one to that one. And only in a single parsha may one not precede the later verse to the earlier one, because it is written "and they shall be." But in the parsha of tzitzit, why should it be a requirement? And perhaps since the two parshiot are required by Torah law, the rabbis ordained it also for the third. And it requires further study.

If one read a parasha and erred in it: if he knows where he erred, such as if he read it all but skipped one verse in the middle – he returns to the beginning of that verse. Even if the omission was in the middle of the verse, nevertheless he returns to the beginning of the verse, and says from there onward until the end of the parasha. And if he does not know where he erred – he returns to the beginning of the parasha. And if he does not know if he also said "Shema Yisrael" – he returns to "Shema Yisrael." And if he knows that he said "Shema Yisrael," and the doubt is from there onward – he begins from "Ve'ahavta," or from "Baruch shem kevod malkhuto le'olam va'ed" if he is in doubt whether he said it. And even though it has already been explained that in a case of doubt regarding "Baruch shem kevod malkhuto le'olam va'ed" he does not need to return – that is when he definitely said "Ve'ahavta." But when he must return to "Ve'ahavta" because of the doubt – he automatically returns also to "Baruch shem kevod malkhuto le'olam va'ed" when there is also a doubt regarding it.

And likewise, if one erred between one parasha and another parasha, such that he knows he finished a parasha but does not know if it was the first or the second—he returns to the first parasha and begins "And it shall come to pass if you surely hearken." And if he was standing at words that are similar in the two parashiot, such as "and you shall write them," "and you shall bind them," "and when you sit in your house," and he does not know if he is in the first or in the second—he returns to that which is in the first. And this is specifically when he has not begun "so that your days may be multiplied." But if he began "so that your days may be multiplied"—it is certainly from the second, for presumably he speaks according to his habit. And all the more so if he knows that he began the parasha of tzitzit—it is certainly from the second. And likewise, if he knows clearly which word he said—there is a presumption that he said everything preceding it, and he only returns to the beginning of the verse of that word.

And not only regarding the recitation of Shema does one return when he has erred. Rather, even in its blessings, when he deviated from the formula established by the sages in any of the blessings—he returns to the beginning of the blessing (the Rambam, chapter one). However, this is specifically when he deviated in the opening or in the conclusion. But if he added some words in the middle of the blessing, or omitted some words—it is of no consequence, since the opening and the conclusion were appropriate. And we have already explained this in siman 59.