98. Communicating During Shema

17:5 The Shema must be read with great care from a siddur; one should be able to hear the words he is reciting. Grammatically, one must not pronounce a Hebrew word as if it has a dagesh where it doesn’t, or vice versa. One should also pause briefly wherever a vertical line is drawn in the text. All of this is equally true in the case of pesukei d’zimrah. One must be especially careful not to mispronounce such words as nishba ("swore") as nishbo ("captured") or u'zchartem ("you shall remember") as u'schartem ("you shall profit").

17:6 Not only should one who is saying Shema not interrupt with speech, he should not communicate through silently moving his lips, nor through winks or gestures. For the sake of a mitzvah, one may communicate through gestures after completing the first paragraph of Shema.