 And thus Rabbi Johanan said in the name of Rabbi Simeon ben Yohai that even people who read just the "Shema" morning and evening thereby fulfill the precept of Rabbi Johanan taught that it is forbidden, however, to teach this to people who through ignorance are careless in the observance of the laws (as it might deter them from further Torah study).But Rava taught that it is meritorious to say it in their presence (as they might think that if merely reciting the "Shema" twice daily earns reward, how great would the reward be for devoting more time to Torah study).A Midrash warned that if one changed the Hebrew letter "dalet" () in the word , "echad" ("one") in into the letter "resh" () (changing the word from "one" to "strange") one could cause the destruction of the Universe.