There is a Mitzvas Asei Min HaTorah, a Biblical Mitzvah, to read the Shema on time, Beschochbecho Uvkumecho, in the morning and in the evening. There is a set time by when Kriyas Shema has to be recited. Even if one is davening Shacharis later, the Shema should be recited before three Halachic hours have passed from the day, what is otherwise known as Soif Zman Krias Shema. The Mishna in Pirkei Ovois says Shina Shel Shacharis, sleep in the morning, is one of those things that Moitziin Es HoOdom Min HoOilam, take a person out of this world. One of the reasons for this is that if one sleeps in the morning, one could chas veSholom miss the Zman Krias Shema, the appropriate time to recite the Shema. The Zohar has very sharp words for someone who loses out on the extremely important Biblical Mitzvah of saying the Shema on time. This is a Biblical Mitzvah as significant as eating Matzah on the first night of Pesach or blowing Shofar on the first day of Rosh Hashana. The Zohar says that there were people who were involved in a Mitzvah, and because of that they could not say the Shema on time. Nevertheless, even though they were exempt from saying the Shema on time because they were involved in a Mitzvah, it had an effect on them, which was even noticeable on the scent from their clothing.