95. Interrupting in the Middle of a Section of Shema

16:4 If one is in the middle of the blessings on either side of Shema, he should pace himself so that his interruptions to answer the various prayers fall between the topics of the blessings. If he saying Shema itself, he should pace himself so that his replies fall between the verses. If this is not possible, one may interrupt in the middle of the verse but he must then recite the verse again starting at the beginning. (Similar to this, Mishnah Brurah 66:10 says that if one cannot reach the break between topics in a bracha, he may rely on the opinions that permit interrupting mid-topic.)

16:5 One may not interrupt in the verses of “Shema Yisrael” and “Baruch Sheim” (or in-between them – MB 66:11) for any reason, even if greeted by an important person. (Exception: you can greet someone who would kill you for not doing so, as per OC 66:1.) One may likewise not interrupt between the conclusion “Ani Hashem Elokeichem” and the word “Emes” that begins the next paragraph. This is because it is meant to paraphrase the verse in Jeremiah (10:10) which states that Hashem our God is true. One should also not interrupt between the words “emes” and “v’yatziv” since yatziv (“firm” or “enduring”) is also an expression of truth. After v’yatziv, one may interrupt as in other places. Formerly, people were permitted to interrupt to extend or return greetings but doing so is no longer considered so imperative as to require interrupting Shema.